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llvm-6502/test/CodeGen/X86/cttz-ctlz.ll

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[CodeGenPrepare] Teach when it is profitable to speculate calls to @llvm.cttz/ctlz. If the control flow is modelling an if-statement where the only instruction in the 'then' basic block (excluding the terminator) is a call to cttz/ctlz, CodeGenPrepare can try to speculate the cttz/ctlz call and simplify the control flow graph. Example: \code entry: %cmp = icmp eq i64 %val, 0 br i1 %cmp, label %end.bb, label %then.bb then.bb: %c = tail call i64 @llvm.cttz.i64(i64 %val, i1 true) br label %end.bb end.bb: %cond = phi i64 [ %c, %then.bb ], [ 64, %entry] \code In this example, basic block %then.bb is taken if value %val is not zero. Also, the phi node in %end.bb would propagate the size-of in bits of %val only if %val is equal to zero. With this patch, CodeGenPrepare will try to hoist the call to cttz from %then.bb into basic block %entry only if cttz is cheap to speculate for the target. Added two new hooks in TargetLowering.h to let targets customize the behavior (i.e. decide whether it is cheap or not to speculate calls to cttz/ctlz). The two new methods are 'isCheapToSpeculateCtlz' and 'isCheapToSpeculateCttz'. By default, both methods return 'false'. On X86, method 'isCheapToSpeculateCtlz' returns true only if the target has LZCNT. Method 'isCheapToSpeculateCttz' only returns true if the target has BMI. Differential Revision: http://reviews.llvm.org/D6728 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224899 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-28 11:07:35 +00:00
; RUN: opt -S -codegenprepare -mtriple=x86_64-unknown-unknown -mattr=+bmi < %s | FileCheck %s --check-prefix=ALL --check-prefix=BMI
; RUN: opt -S -codegenprepare -mtriple=x86_64-unknown-unknown -mattr=+lzcnt < %s | FileCheck %s --check-prefix=ALL --check-prefix=LZCNT
; RUN: opt -S -codegenprepare -mtriple=x86_64-unknown-unknown < %s | FileCheck %s --check-prefix=ALL --check-prefix=GENERIC
define i64 @test1(i64 %A) {
; ALL-LABEL: @test1(
; LZCNT: [[CTLZ:%[A-Za-z0-9]+]] = call i64 @llvm.ctlz.i64(i64 %A, i1 false)
; LZCNT-NEXT: ret i64 [[CTLZ]]
; BMI: icmp eq i64 %A, 0
; BMI: call i64 @llvm.ctlz.i64(i64 %A, i1 true)
; GENERIC: icmp eq i64 %A, 0
; GENERIC: call i64 @llvm.ctlz.i64(i64 %A, i1 true)
entry:
%tobool = icmp eq i64 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
ret i64 %cond
}
define i32 @test2(i32 %A) {
; ALL-LABEL: @test2(
; LZCNT: [[CTLZ:%[A-Za-z0-9]+]] = call i32 @llvm.ctlz.i32(i32 %A, i1 false)
; LZCNT-NEXT: ret i32 [[CTLZ]]
; BMI: icmp eq i32 %A, 0
; BMI: call i32 @llvm.ctlz.i32(i32 %A, i1 true)
; GENERIC: icmp eq i32 %A, 0
; GENERIC: call i32 @llvm.ctlz.i32(i32 %A, i1 true)
entry:
%tobool = icmp eq i32 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
ret i32 %cond
}
define signext i16 @test3(i16 signext %A) {
; ALL-LABEL: @test3(
; LZCNT: [[CTLZ:%[A-Za-z0-9]+]] = call i16 @llvm.ctlz.i16(i16 %A, i1 false)
; LZCNT-NEXT: ret i16 [[CTLZ]]
; BMI: icmp eq i16 %A, 0
; BMI: call i16 @llvm.ctlz.i16(i16 %A, i1 true)
; GENERIC: icmp eq i16 %A, 0
; GENERIC: call i16 @llvm.ctlz.i16(i16 %A, i1 true)
entry:
%tobool = icmp eq i16 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
ret i16 %cond
}
define i64 @test1b(i64 %A) {
; ALL-LABEL: @test1b(
; LZCNT: icmp eq i64 %A, 0
; LZCNT: call i64 @llvm.cttz.i64(i64 %A, i1 true)
; BMI: [[CTTZ:%[A-Za-z0-9]+]] = call i64 @llvm.cttz.i64(i64 %A, i1 false)
; BMI-NEXT: ret i64 [[CTTZ]]
; GENERIC: icmp eq i64 %A, 0
; GENERIC: call i64 @llvm.cttz.i64(i64 %A, i1 true)
entry:
%tobool = icmp eq i64 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %0, %cond.true ], [ 64, %entry ]
ret i64 %cond
}
define i32 @test2b(i32 %A) {
; ALL-LABEL: @test2b(
; LZCNT: icmp eq i32 %A, 0
; LZCNT: call i32 @llvm.cttz.i32(i32 %A, i1 true)
; BMI: [[CTTZ:%[A-Za-z0-9]+]] = call i32 @llvm.cttz.i32(i32 %A, i1 false)
; BMI-NEXT: ret i32 [[CTTZ]]
; GENERIC: icmp eq i32 %A, 0
; GENERIC: call i32 @llvm.cttz.i32(i32 %A, i1 true)
entry:
%tobool = icmp eq i32 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %0, %cond.true ], [ 32, %entry ]
ret i32 %cond
}
define signext i16 @test3b(i16 signext %A) {
; ALL-LABEL: @test3b(
; LZCNT: icmp eq i16 %A, 0
; LZCNT: call i16 @llvm.cttz.i16(i16 %A, i1 true)
; BMI: [[CTTZ:%[A-Za-z0-9]+]] = call i16 @llvm.cttz.i16(i16 %A, i1 false)
; BMI-NEXT: ret i16 [[CTTZ]]
; GENERIC: icmp eq i16 %A, 0
; GENERIC: call i16 @llvm.cttz.i16(i16 %A, i1 true)
entry:
%tobool = icmp eq i16 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %0, %cond.true ], [ 16, %entry ]
ret i16 %cond
}
define i64 @test1c(i64 %A) {
; ALL-LABEL: @test1c(
; ALL: icmp eq i64 %A, 0
; ALL: call i64 @llvm.ctlz.i64(i64 %A, i1 true)
entry:
%tobool = icmp eq i64 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.ctlz.i64(i64 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %0, %cond.true ], [ 63, %entry ]
ret i64 %cond
}
define i32 @test2c(i32 %A) {
; ALL-LABEL: @test2c(
; ALL: icmp eq i32 %A, 0
; ALL: call i32 @llvm.ctlz.i32(i32 %A, i1 true)
entry:
%tobool = icmp eq i32 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.ctlz.i32(i32 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %0, %cond.true ], [ 31, %entry ]
ret i32 %cond
}
define signext i16 @test3c(i16 signext %A) {
; ALL-LABEL: @test3c(
; ALL: icmp eq i16 %A, 0
; ALL: call i16 @llvm.ctlz.i16(i16 %A, i1 true)
entry:
%tobool = icmp eq i16 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i16 @llvm.ctlz.i16(i16 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %0, %cond.true ], [ 15, %entry ]
ret i16 %cond
}
define i64 @test1d(i64 %A) {
; ALL-LABEL: @test1d(
; ALL: icmp eq i64 %A, 0
; ALL: call i64 @llvm.cttz.i64(i64 %A, i1 true)
entry:
%tobool = icmp eq i64 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.cttz.i64(i64 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %0, %cond.true ], [ 63, %entry ]
ret i64 %cond
}
define i32 @test2d(i32 %A) {
; ALL-LABEL: @test2d(
; ALL: icmp eq i32 %A, 0
; ALL: call i32 @llvm.cttz.i32(i32 %A, i1 true)
entry:
%tobool = icmp eq i32 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.cttz.i32(i32 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %0, %cond.true ], [ 31, %entry ]
ret i32 %cond
}
define signext i16 @test3d(i16 signext %A) {
; ALL-LABEL: @test3d(
; ALL: icmp eq i16 %A, 0
; ALL: call i16 @llvm.cttz.i16(i16 %A, i1 true)
entry:
%tobool = icmp eq i16 %A, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i16 @llvm.cttz.i16(i16 %A, i1 true)
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %0, %cond.true ], [ 15, %entry ]
ret i16 %cond
}
[CodeGenPrepare] Improved logic to speculate calls to cttz/ctlz. This patch improves the logic added at revision 224899 (see review D6728) that teaches the backend when it is profitable to speculate calls to cttz/ctlz. The original algorithm conservatively avoided speculating more than one instruction from a basic block in a control flow grap modelling an if-statement. In particular, the only allowed instruction (excluding the terminator) was a call to cttz/ctlz. However, there are cases where we could be less conservative and still be able to speculate a call to cttz/ctlz. With this patch, CodeGenPrepare now tries to speculate a cttz/ctlz if the result is zero extended/truncated in the same basic block, and the zext/trunc instruction is "free" for the target. Added new test cases to CodeGen/X86/cttz-ctlz.ll Differential Revision: http://reviews.llvm.org/D6853 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@225274 91177308-0d34-0410-b5e6-96231b3b80d8
2015-01-06 17:41:18 +00:00
; The following tests verify that calls to cttz/ctlz are speculated even if
; basic block %cond.true has an extra zero extend/truncate which is "free"
; for the target.
define i64 @test1e(i32 %x) {
; ALL-LABEL: @test1e(
; LZCNT: icmp eq i32 %x, 0
; LZCNT: call i32 @llvm.cttz.i32(i32 %x, i1 true)
; BMI: call i32 @llvm.cttz.i32(i32 %x, i1 false)
; GENERIC: icmp eq i32 %x, 0
; GENERIC: call i32 @llvm.cttz.i32(i32 %x, i1 true)
entry:
%tobool = icmp eq i32 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
%phitmp2 = zext i32 %0 to i64
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %phitmp2, %cond.true ], [ 32, %entry ]
ret i64 %cond
}
define i32 @test2e(i64 %x) {
; ALL-LABEL: @test2e(
; LZCNT: icmp eq i64 %x, 0
; LZCNT: call i64 @llvm.cttz.i64(i64 %x, i1 true)
; BMI: call i64 @llvm.cttz.i64(i64 %x, i1 false)
; GENERIC: icmp eq i64 %x, 0
; GENERIC: call i64 @llvm.cttz.i64(i64 %x, i1 true)
entry:
%tobool = icmp eq i64 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.cttz.i64(i64 %x, i1 true)
%cast = trunc i64 %0 to i32
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %cast, %cond.true ], [ 64, %entry ]
ret i32 %cond
}
define i64 @test3e(i32 %x) {
; ALL-LABEL: @test3e(
; BMI: icmp eq i32 %x, 0
; BMI: call i32 @llvm.ctlz.i32(i32 %x, i1 true)
; LZCNT: call i32 @llvm.ctlz.i32(i32 %x, i1 false)
; GENERIC: icmp eq i32 %x, 0
; GENERIC: call i32 @llvm.ctlz.i32(i32 %x, i1 true)
entry:
%tobool = icmp eq i32 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.ctlz.i32(i32 %x, i1 true)
%phitmp2 = zext i32 %0 to i64
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i64 [ %phitmp2, %cond.true ], [ 32, %entry ]
ret i64 %cond
}
define i32 @test4e(i64 %x) {
; ALL-LABEL: @test4e(
; BMI: icmp eq i64 %x, 0
; BMI: call i64 @llvm.ctlz.i64(i64 %x, i1 true)
; LZCNT: call i64 @llvm.ctlz.i64(i64 %x, i1 false)
; GENERIC: icmp eq i64 %x, 0
; GENERIC: call i64 @llvm.ctlz.i64(i64 %x, i1 true)
entry:
%tobool = icmp eq i64 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.ctlz.i64(i64 %x, i1 true)
%cast = trunc i64 %0 to i32
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i32 [ %cast, %cond.true ], [ 64, %entry ]
ret i32 %cond
}
define i16 @test5e(i64 %x) {
; ALL-LABEL: @test5e(
; BMI: icmp eq i64 %x, 0
; BMI: call i64 @llvm.ctlz.i64(i64 %x, i1 true)
; LZCNT: call i64 @llvm.ctlz.i64(i64 %x, i1 false)
; GENERIC: icmp eq i64 %x, 0
; GENERIC: call i64 @llvm.ctlz.i64(i64 %x, i1 true)
entry:
%tobool = icmp eq i64 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.ctlz.i64(i64 %x, i1 true)
%cast = trunc i64 %0 to i16
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %cast, %cond.true ], [ 64, %entry ]
ret i16 %cond
}
define i16 @test6e(i32 %x) {
; ALL-LABEL: @test6e(
; BMI: icmp eq i32 %x, 0
; BMI: call i32 @llvm.ctlz.i32(i32 %x, i1 true)
; LZCNT: call i32 @llvm.ctlz.i32(i32 %x, i1 false)
; GENERIC: icmp eq i32 %x, 0
; GENERIC: call i32 @llvm.ctlz.i32(i32 %x, i1 true)
entry:
%tobool = icmp eq i32 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.ctlz.i32(i32 %x, i1 true)
%cast = trunc i32 %0 to i16
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %cast, %cond.true ], [ 32, %entry ]
ret i16 %cond
}
define i16 @test7e(i64 %x) {
; ALL-LABEL: @test7e(
; LZCNT: icmp eq i64 %x, 0
; LZCNT: call i64 @llvm.cttz.i64(i64 %x, i1 true)
; BMI: call i64 @llvm.cttz.i64(i64 %x, i1 false)
; GENERIC: icmp eq i64 %x, 0
; GENERIC: call i64 @llvm.cttz.i64(i64 %x, i1 true)
entry:
%tobool = icmp eq i64 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i64 @llvm.cttz.i64(i64 %x, i1 true)
%cast = trunc i64 %0 to i16
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %cast, %cond.true ], [ 64, %entry ]
ret i16 %cond
}
define i16 @test8e(i32 %x) {
; ALL-LABEL: @test8e(
; LZCNT: icmp eq i32 %x, 0
; LZCNT: call i32 @llvm.cttz.i32(i32 %x, i1 true)
; BMI: call i32 @llvm.cttz.i32(i32 %x, i1 false)
; GENERIC: icmp eq i32 %x, 0
; GENERIC: call i32 @llvm.cttz.i32(i32 %x, i1 true)
entry:
%tobool = icmp eq i32 %x, 0
br i1 %tobool, label %cond.end, label %cond.true
cond.true: ; preds = %entry
%0 = tail call i32 @llvm.cttz.i32(i32 %x, i1 true)
%cast = trunc i32 %0 to i16
br label %cond.end
cond.end: ; preds = %entry, %cond.true
%cond = phi i16 [ %cast, %cond.true ], [ 32, %entry ]
ret i16 %cond
}
[CodeGenPrepare] Teach when it is profitable to speculate calls to @llvm.cttz/ctlz. If the control flow is modelling an if-statement where the only instruction in the 'then' basic block (excluding the terminator) is a call to cttz/ctlz, CodeGenPrepare can try to speculate the cttz/ctlz call and simplify the control flow graph. Example: \code entry: %cmp = icmp eq i64 %val, 0 br i1 %cmp, label %end.bb, label %then.bb then.bb: %c = tail call i64 @llvm.cttz.i64(i64 %val, i1 true) br label %end.bb end.bb: %cond = phi i64 [ %c, %then.bb ], [ 64, %entry] \code In this example, basic block %then.bb is taken if value %val is not zero. Also, the phi node in %end.bb would propagate the size-of in bits of %val only if %val is equal to zero. With this patch, CodeGenPrepare will try to hoist the call to cttz from %then.bb into basic block %entry only if cttz is cheap to speculate for the target. Added two new hooks in TargetLowering.h to let targets customize the behavior (i.e. decide whether it is cheap or not to speculate calls to cttz/ctlz). The two new methods are 'isCheapToSpeculateCtlz' and 'isCheapToSpeculateCttz'. By default, both methods return 'false'. On X86, method 'isCheapToSpeculateCtlz' returns true only if the target has LZCNT. Method 'isCheapToSpeculateCttz' only returns true if the target has BMI. Differential Revision: http://reviews.llvm.org/D6728 git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@224899 91177308-0d34-0410-b5e6-96231b3b80d8
2014-12-28 11:07:35 +00:00
declare i64 @llvm.ctlz.i64(i64, i1)
declare i32 @llvm.ctlz.i32(i32, i1)
declare i16 @llvm.ctlz.i16(i16, i1)
declare i64 @llvm.cttz.i64(i64, i1)
declare i32 @llvm.cttz.i32(i32, i1)
declare i16 @llvm.cttz.i16(i16, i1)
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