[PowerPC] Select between VSX A-type and M-type FMA instructions just before RA
The VSX instruction set has two types of FMA instructions: A-type (where the
addend is taken from the output register) and M-type (where one of the product
operands is taken from the output register). This adds a small pass that runs
just after MI scheduling (and, thus, just before register allocation) that
mutates A-type instructions (that are created during isel) into M-type
instructions when:
1. This will eliminate an otherwise-necessary copy of the addend
2. One of the product operands is killed by the instruction
The "right" moment to make this decision is in between scheduling and register
allocation, because only there do we know whether or not one of the product
operands is killed by any particular instruction. Unfortunately, this also
makes the implementation somewhat complicated, because the MIs are not in SSA
form and we need to preserve the LiveIntervals analysis.
As a simple example, if we have:
%vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
...
%vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
%RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
...
We can eliminate the copy by changing from the A-type to the
M-type instruction. This means:
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
is replaced by:
%vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
%RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204768 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 23:29:21 +00:00
|
|
|
; RUN: llc < %s -mcpu=pwr7 -mattr=+vsx | FileCheck %s
|
|
|
|
|
|
|
|
; Also run with -schedule-ppc-vsx-fma-mutation-early as a stress test for the
|
|
|
|
; live-interval-updating logic.
|
|
|
|
; RUN: llc < %s -mcpu=pwr7 -mattr=+vsx -schedule-ppc-vsx-fma-mutation-early
|
|
|
|
target datalayout = "E-m:e-i64:64-n32:64"
|
|
|
|
target triple = "powerpc64-unknown-linux-gnu"
|
|
|
|
|
|
|
|
define void @test1(double %a, double %b, double %c, double %e, double* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call double @llvm.fma.f64(double %b, double %c, double %a)
|
|
|
|
store double %0, double* %d, align 8
|
|
|
|
%1 = tail call double @llvm.fma.f64(double %b, double %e, double %a)
|
|
|
|
%arrayidx1 = getelementptr inbounds double* %d, i64 1
|
|
|
|
store double %1, double* %arrayidx1, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @test1
|
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 8
|
|
|
|
; CHECK-DAG: xsmaddmdp 3, 2, 1
|
|
|
|
; CHECK-DAG: xsmaddadp 1, 2, 4
|
|
|
|
; CHECK-DAG: stxsdx 3, 0, 7
|
|
|
|
; CHECK-DAG: stxsdx 1, 7, [[C1]]
|
|
|
|
; CHECK: blr
|
|
|
|
}
|
|
|
|
|
|
|
|
define void @test2(double %a, double %b, double %c, double %e, double %f, double* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call double @llvm.fma.f64(double %b, double %c, double %a)
|
|
|
|
store double %0, double* %d, align 8
|
|
|
|
%1 = tail call double @llvm.fma.f64(double %b, double %e, double %a)
|
|
|
|
%arrayidx1 = getelementptr inbounds double* %d, i64 1
|
|
|
|
store double %1, double* %arrayidx1, align 8
|
|
|
|
%2 = tail call double @llvm.fma.f64(double %b, double %f, double %a)
|
|
|
|
%arrayidx2 = getelementptr inbounds double* %d, i64 2
|
|
|
|
store double %2, double* %arrayidx2, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @test2
|
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 8
|
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|
|
; CHECK-DAG: li [[C2:[0-9]+]], 16
|
|
|
|
; CHECK-DAG: xsmaddmdp 3, 2, 1
|
|
|
|
; CHECK-DAG: xsmaddmdp 4, 2, 1
|
|
|
|
; CHECK-DAG: xsmaddadp 1, 2, 5
|
|
|
|
; CHECK-DAG: stxsdx 3, 0, 8
|
|
|
|
; CHECK-DAG: stxsdx 4, 8, [[C1]]
|
|
|
|
; CHECK-DAG: stxsdx 1, 8, [[C2]]
|
|
|
|
; CHECK: blr
|
|
|
|
}
|
|
|
|
|
|
|
|
define void @test3(double %a, double %b, double %c, double %e, double %f, double* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call double @llvm.fma.f64(double %b, double %c, double %a)
|
|
|
|
store double %0, double* %d, align 8
|
|
|
|
%1 = tail call double @llvm.fma.f64(double %b, double %e, double %a)
|
|
|
|
%2 = tail call double @llvm.fma.f64(double %b, double %c, double %1)
|
|
|
|
%arrayidx1 = getelementptr inbounds double* %d, i64 3
|
|
|
|
store double %2, double* %arrayidx1, align 8
|
|
|
|
%3 = tail call double @llvm.fma.f64(double %b, double %f, double %a)
|
|
|
|
%arrayidx2 = getelementptr inbounds double* %d, i64 2
|
|
|
|
store double %3, double* %arrayidx2, align 8
|
|
|
|
%arrayidx3 = getelementptr inbounds double* %d, i64 1
|
|
|
|
store double %1, double* %arrayidx3, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @test3
|
2014-03-29 05:29:01 +00:00
|
|
|
; CHECK-DAG: fmr [[F1:[0-9]+]], 1
|
[PowerPC] Select between VSX A-type and M-type FMA instructions just before RA
The VSX instruction set has two types of FMA instructions: A-type (where the
addend is taken from the output register) and M-type (where one of the product
operands is taken from the output register). This adds a small pass that runs
just after MI scheduling (and, thus, just before register allocation) that
mutates A-type instructions (that are created during isel) into M-type
instructions when:
1. This will eliminate an otherwise-necessary copy of the addend
2. One of the product operands is killed by the instruction
The "right" moment to make this decision is in between scheduling and register
allocation, because only there do we know whether or not one of the product
operands is killed by any particular instruction. Unfortunately, this also
makes the implementation somewhat complicated, because the MIs are not in SSA
form and we need to preserve the LiveIntervals analysis.
As a simple example, if we have:
%vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
...
%vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
%RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
...
We can eliminate the copy by changing from the A-type to the
M-type instruction. This means:
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
is replaced by:
%vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
%RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204768 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 23:29:21 +00:00
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 24
|
|
|
|
; CHECK-DAG: li [[C2:[0-9]+]], 16
|
|
|
|
; CHECK-DAG: li [[C3:[0-9]+]], 8
|
|
|
|
; CHECK-DAG: xsmaddmdp 4, 2, 1
|
|
|
|
; CHECK-DAG: xsmaddadp 1, 2, 5
|
|
|
|
|
|
|
|
; Note: We could convert this next FMA to M-type as well, but it would require
|
|
|
|
; re-ordering the instructions.
|
|
|
|
; CHECK-DAG: xsmaddadp [[F1]], 2, 3
|
|
|
|
|
|
|
|
; CHECK-DAG: xsmaddmdp 2, 3, 4
|
|
|
|
; CHECK-DAG: stxsdx [[F1]], 0, 8
|
|
|
|
; CHECK-DAG: stxsdx 2, 8, [[C1]]
|
|
|
|
; CHECK-DAG: stxsdx 1, 8, [[C2]]
|
|
|
|
; CHECK-DAG: stxsdx 4, 8, [[C3]]
|
2014-03-29 05:29:01 +00:00
|
|
|
; CHECK: blr
|
[PowerPC] Select between VSX A-type and M-type FMA instructions just before RA
The VSX instruction set has two types of FMA instructions: A-type (where the
addend is taken from the output register) and M-type (where one of the product
operands is taken from the output register). This adds a small pass that runs
just after MI scheduling (and, thus, just before register allocation) that
mutates A-type instructions (that are created during isel) into M-type
instructions when:
1. This will eliminate an otherwise-necessary copy of the addend
2. One of the product operands is killed by the instruction
The "right" moment to make this decision is in between scheduling and register
allocation, because only there do we know whether or not one of the product
operands is killed by any particular instruction. Unfortunately, this also
makes the implementation somewhat complicated, because the MIs are not in SSA
form and we need to preserve the LiveIntervals analysis.
As a simple example, if we have:
%vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
...
%vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
%RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
...
We can eliminate the copy by changing from the A-type to the
M-type instruction. This means:
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
is replaced by:
%vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
%RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204768 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 23:29:21 +00:00
|
|
|
}
|
|
|
|
|
|
|
|
define void @test4(double %a, double %b, double %c, double %e, double %f, double* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call double @llvm.fma.f64(double %b, double %c, double %a)
|
|
|
|
store double %0, double* %d, align 8
|
|
|
|
%1 = tail call double @llvm.fma.f64(double %b, double %e, double %a)
|
|
|
|
%arrayidx1 = getelementptr inbounds double* %d, i64 1
|
|
|
|
store double %1, double* %arrayidx1, align 8
|
|
|
|
%2 = tail call double @llvm.fma.f64(double %b, double %c, double %1)
|
|
|
|
%arrayidx3 = getelementptr inbounds double* %d, i64 3
|
|
|
|
store double %2, double* %arrayidx3, align 8
|
|
|
|
%3 = tail call double @llvm.fma.f64(double %b, double %f, double %a)
|
|
|
|
%arrayidx4 = getelementptr inbounds double* %d, i64 2
|
|
|
|
store double %3, double* %arrayidx4, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @test4
|
2014-03-29 05:29:01 +00:00
|
|
|
; CHECK-DAG: fmr [[F1:[0-9]+]], 1
|
[PowerPC] Select between VSX A-type and M-type FMA instructions just before RA
The VSX instruction set has two types of FMA instructions: A-type (where the
addend is taken from the output register) and M-type (where one of the product
operands is taken from the output register). This adds a small pass that runs
just after MI scheduling (and, thus, just before register allocation) that
mutates A-type instructions (that are created during isel) into M-type
instructions when:
1. This will eliminate an otherwise-necessary copy of the addend
2. One of the product operands is killed by the instruction
The "right" moment to make this decision is in between scheduling and register
allocation, because only there do we know whether or not one of the product
operands is killed by any particular instruction. Unfortunately, this also
makes the implementation somewhat complicated, because the MIs are not in SSA
form and we need to preserve the LiveIntervals analysis.
As a simple example, if we have:
%vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
...
%vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
%RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
...
We can eliminate the copy by changing from the A-type to the
M-type instruction. This means:
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
is replaced by:
%vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
%RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204768 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 23:29:21 +00:00
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 8
|
|
|
|
; CHECK-DAG: li [[C2:[0-9]+]], 16
|
|
|
|
; CHECK-DAG: xsmaddmdp 4, 2, 1
|
|
|
|
|
|
|
|
; Note: We could convert this next FMA to M-type as well, but it would require
|
|
|
|
; re-ordering the instructions.
|
|
|
|
; CHECK-DAG: xsmaddadp 1, 2, 5
|
|
|
|
|
|
|
|
; CHECK-DAG: xsmaddadp [[F1]], 2, 3
|
|
|
|
; CHECK-DAG: stxsdx [[F1]], 0, 8
|
|
|
|
; CHECK-DAG: stxsdx 4, 8, [[C1]]
|
|
|
|
; CHECK-DAG: li [[C3:[0-9]+]], 24
|
|
|
|
; CHECK-DAG: xsmaddadp 4, 2, 3
|
|
|
|
; CHECK-DAG: stxsdx 4, 8, [[C3]]
|
|
|
|
; CHECK-DAG: stxsdx 1, 8, [[C2]]
|
|
|
|
; CHECK: blr
|
|
|
|
}
|
|
|
|
|
|
|
|
declare double @llvm.fma.f64(double, double, double) #0
|
|
|
|
|
2014-03-29 05:29:01 +00:00
|
|
|
define void @testv1(<2 x double> %a, <2 x double> %b, <2 x double> %c, <2 x double> %e, <2 x double>* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %a)
|
|
|
|
store <2 x double> %0, <2 x double>* %d, align 8
|
|
|
|
%1 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %e, <2 x double> %a)
|
|
|
|
%arrayidx1 = getelementptr inbounds <2 x double>* %d, i64 1
|
|
|
|
store <2 x double> %1, <2 x double>* %arrayidx1, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @testv1
|
|
|
|
; CHECK-DAG: xvmaddmdp 36, 35, 34
|
|
|
|
; CHECK-DAG: xvmaddadp 34, 35, 37
|
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 16
|
|
|
|
; CHECK-DAG: stxvd2x 36, 0, 3
|
|
|
|
; CHECK-DAG: stxvd2x 34, 3, [[C1:[0-9]+]]
|
|
|
|
; CHECK: blr
|
|
|
|
}
|
|
|
|
|
|
|
|
define void @testv2(<2 x double> %a, <2 x double> %b, <2 x double> %c, <2 x double> %e, <2 x double> %f, <2 x double>* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %a)
|
|
|
|
store <2 x double> %0, <2 x double>* %d, align 8
|
|
|
|
%1 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %e, <2 x double> %a)
|
|
|
|
%arrayidx1 = getelementptr inbounds <2 x double>* %d, i64 1
|
|
|
|
store <2 x double> %1, <2 x double>* %arrayidx1, align 8
|
|
|
|
%2 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %f, <2 x double> %a)
|
|
|
|
%arrayidx2 = getelementptr inbounds <2 x double>* %d, i64 2
|
|
|
|
store <2 x double> %2, <2 x double>* %arrayidx2, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @testv2
|
|
|
|
; CHECK-DAG: xvmaddmdp 36, 35, 34
|
|
|
|
; CHECK-DAG: xvmaddmdp 37, 35, 34
|
|
|
|
; CHECK-DAG: li [[C1:[0-9]+]], 16
|
|
|
|
; CHECK-DAG: li [[C2:[0-9]+]], 32
|
|
|
|
; CHECK-DAG: xvmaddadp 34, 35, 38
|
|
|
|
; CHECK-DAG: stxvd2x 36, 0, 3
|
|
|
|
; CHECK-DAG: stxvd2x 37, 3, [[C1:[0-9]+]]
|
|
|
|
; CHECK-DAG: stxvd2x 34, 3, [[C2:[0-9]+]]
|
|
|
|
; CHECK: blr
|
|
|
|
}
|
|
|
|
|
|
|
|
define void @testv3(<2 x double> %a, <2 x double> %b, <2 x double> %c, <2 x double> %e, <2 x double> %f, <2 x double>* nocapture %d) #0 {
|
|
|
|
entry:
|
|
|
|
%0 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %a)
|
|
|
|
store <2 x double> %0, <2 x double>* %d, align 8
|
|
|
|
%1 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %e, <2 x double> %a)
|
|
|
|
%2 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %1)
|
|
|
|
%arrayidx1 = getelementptr inbounds <2 x double>* %d, i64 3
|
|
|
|
store <2 x double> %2, <2 x double>* %arrayidx1, align 8
|
|
|
|
%3 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %f, <2 x double> %a)
|
|
|
|
%arrayidx2 = getelementptr inbounds <2 x double>* %d, i64 2
|
|
|
|
store <2 x double> %3, <2 x double>* %arrayidx2, align 8
|
|
|
|
%arrayidx3 = getelementptr inbounds <2 x double>* %d, i64 1
|
|
|
|
store <2 x double> %1, <2 x double>* %arrayidx3, align 8
|
|
|
|
ret void
|
|
|
|
|
|
|
|
; CHECK-LABEL: @testv3
|
|
|
|
; CHECK-DAG: xxlor [[V1:[0-9]+]], 34, 34
|
|
|
|
; CHECK-DAG: xvmaddmdp 37, 35, 34
|
|
|
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; CHECK-DAG: li [[C1:[0-9]+]], 48
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; CHECK-DAG: li [[C2:[0-9]+]], 32
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; CHECK-DAG: xvmaddadp 34, 35, 38
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; CHECK-DAG: li [[C3:[0-9]+]], 16
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; Note: We could convert this next FMA to M-type as well, but it would require
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; re-ordering the instructions.
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; CHECK-DAG: xvmaddadp [[V1]], 35, 36
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; CHECK-DAG: xvmaddmdp 35, 36, 37
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; CHECK-DAG: stxvd2x 32, 0, 3
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; CHECK-DAG: stxvd2x 35, 3, [[C1]]
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; CHECK-DAG: stxvd2x 34, 3, [[C2]]
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; CHECK-DAG: stxvd2x 37, 3, [[C3]]
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; CHECK: blr
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}
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define void @testv4(<2 x double> %a, <2 x double> %b, <2 x double> %c, <2 x double> %e, <2 x double> %f, <2 x double>* nocapture %d) #0 {
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entry:
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%0 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %a)
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store <2 x double> %0, <2 x double>* %d, align 8
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%1 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %e, <2 x double> %a)
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%arrayidx1 = getelementptr inbounds <2 x double>* %d, i64 1
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store <2 x double> %1, <2 x double>* %arrayidx1, align 8
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%2 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %c, <2 x double> %1)
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%arrayidx3 = getelementptr inbounds <2 x double>* %d, i64 3
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store <2 x double> %2, <2 x double>* %arrayidx3, align 8
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%3 = tail call <2 x double> @llvm.fma.v2f64(<2 x double> %b, <2 x double> %f, <2 x double> %a)
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%arrayidx4 = getelementptr inbounds <2 x double>* %d, i64 2
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store <2 x double> %3, <2 x double>* %arrayidx4, align 8
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ret void
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; CHECK-LABEL: @testv4
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; CHECK-DAG: xxlor [[V1:[0-9]+]], 34, 34
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; CHECK-DAG: xvmaddmdp 37, 35, 34
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; CHECK-DAG: li [[C1:[0-9]+]], 16
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; CHECK-DAG: li [[C2:[0-9]+]], 32
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; CHECK-DAG: xvmaddadp 34, 35, 38
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; Note: We could convert this next FMA to M-type as well, but it would require
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; re-ordering the instructions.
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; CHECK-DAG: xvmaddadp [[V1]], 35, 36
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; CHECK-DAG: stxvd2x 32, 0, 3
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; CHECK-DAG: stxvd2x 37, 3, [[C1]]
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; CHECK-DAG: li [[C3:[0-9]+]], 48
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; CHECK-DAG: xvmaddadp 37, 35, 36
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; CHECK-DAG: stxvd2x 37, 3, [[C3]]
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; CHECK-DAG: stxvd2x 34, 3, [[C2]]
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; CHECK: blr
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}
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declare <2 x double> @llvm.fma.v2f64(<2 x double>, <2 x double>, <2 x double>) #0
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[PowerPC] Select between VSX A-type and M-type FMA instructions just before RA
The VSX instruction set has two types of FMA instructions: A-type (where the
addend is taken from the output register) and M-type (where one of the product
operands is taken from the output register). This adds a small pass that runs
just after MI scheduling (and, thus, just before register allocation) that
mutates A-type instructions (that are created during isel) into M-type
instructions when:
1. This will eliminate an otherwise-necessary copy of the addend
2. One of the product operands is killed by the instruction
The "right" moment to make this decision is in between scheduling and register
allocation, because only there do we know whether or not one of the product
operands is killed by any particular instruction. Unfortunately, this also
makes the implementation somewhat complicated, because the MIs are not in SSA
form and we need to preserve the LiveIntervals analysis.
As a simple example, if we have:
%vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
...
%vreg9<def,tied1> = XSMADDADP %vreg9<tied0>, %vreg17, %vreg19,
%RM<imp-use>; VSLRC:%vreg9,%vreg17,%vreg19
...
We can eliminate the copy by changing from the A-type to the
M-type instruction. This means:
%vreg5<def,tied1> = XSMADDADP %vreg5<tied0>, %vreg17, %vreg16,
%RM<imp-use>; VSLRC:%vreg5,%vreg17,%vreg16
is replaced by:
%vreg16<def,tied1> = XSMADDMDP %vreg16<tied0>, %vreg18, %vreg9,
%RM<imp-use>; VSLRC:%vreg16,%vreg18,%vreg9
and we remove: %vreg5<def> = COPY %vreg9; VSLRC:%vreg5,%vreg9
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@204768 91177308-0d34-0410-b5e6-96231b3b80d8
2014-03-25 23:29:21 +00:00
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attributes #0 = { nounwind readnone }
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