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Reassociate x + -0.1234 * y into x - 0.1234 * y

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This does not require -ffast-math, and it gives CSE/GVN more options to
eliminate duplicate expressions in, e.g.:

  return ((x + 0.1234 * y) * (x - 0.1234 * y));

Differential Revision: http://reviews.llvm.org/D4904



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@216169 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Erik Verbruggen
2014-08-21 10:45:30 +00:00
parent f11ac42d01
commit 0edc5e8391
4 changed files with 119 additions and 41 deletions
Download Patch File Download Diff File Expand all files Collapse all files
test/Transforms/Reassociate/fast-basictest.ll
+1 -1
View File
@@ -193,7 +193,7 @@ define float @test13(float %X1, float %X2, float %X3) {
define float @test14(float %X1, float %X2) {
; CHECK-LABEL: @test14
; CHECK-NEXT: fsub fast float %X1, %X2
; CHECK-NEXT: fmul fast float %tmp, 4.700000e+01
; CHECK-NEXT: fmul fast float %1, 4.700000e+01
; CHECK-NEXT: ret float
%B = fmul fast float %X1, 47. ; X1*47
test/Transforms/Reassociate/liftsign.ll
+69
View File
@@ -0,0 +1,69 @@
; RUN: opt -reassociate -gvn -S < %s | FileCheck %s
; (x + 0.1234 * y) * (x + -0.1234 * y) -> (x + 0.1234 * y) * (x - 0.1234 * y)
; so CSE can simplify it further
define double @lift_sign1(double %x, double %y) nounwind readnone ssp uwtable {
; CHECK-LABEL: @lift_sign1(
%mul = fmul double 1.234000e-01, %y
%add = fadd double %mul, %x
%mul1 = fmul double -1.234000e-01, %y
%add2 = fadd double %mul1, %x
%mul3 = fmul double %add, %add2
; CHECK-NOT: %mul1 = fmul double -1.234000e-01, %y
; CHECK-NOT: %add2 = fadd %mul1, %x
; CHECK: %add2.repl = fsub double %x, %mul
; CHECK: %mul3 = fmul double %add, %add2
ret double %mul3
}
; (x + -0.1234 * y) * (x + -0.1234 * y) -> (x - 0.1234 * y) * (x - 0.1234 * y)
; GVN can then rewrite it even further
define double @lift_sign2(double %x, double %y) nounwind readnone ssp uwtable {
; CHECK-LABEL: @lift_sign2(
%mul = fmul double %y, -1.234000e-01
%add = fadd double %mul, %x
%mul1 = fmul double %y, -1.234000e-01
%add2 = fadd double %mul1, %x
%mul3 = fmul double %add, %add2
; CHECK-NOT: %mul = fmul double %y, -1.234000e-01
; CHECK-NOT: %add = fadd double %mul, %x
; CHECK-NOT: %mul1 = fmul double %y, -1.234000e-01
; CHECK-NOT: %add2 = fadd double %mul1, %x
; CHECK-NOT: %mul3 = fmul double %add, %add2
; CHECK: %mul = fmul double 1.234000e-01, %y
; CHECK: %add.repl = fsub double %x, %mul
; CHECK: %mul3 = fmul double %add.repl, %add.repl
ret double %mul3
}
; (x + 0.1234 * y) * (x - -0.1234 * y) -> (x + 0.1234 * y) * (x + 0.1234 * y)
define double @lift_sign3(double %x, double %y) nounwind readnone ssp uwtable {
; CHECK-LABEL: @lift_sign3(
%mul = fmul double %y, 1.234000e-01
%add = fadd double %mul, %x
%mul1 = fmul double %y, -1.234000e-01
%add2 = fsub double %x, %mul1
%mul3 = fmul double %add, %add2
; CHECK-NOT: %mul1 = fmul double %y, -1.234000e-01
; CHECK-NOT: %add2 = fsub double %x, %mul1
; CHECK-NOT: %mul3 = fmul double %add, %add2
; CHECK: %mul3 = fmul double %add, %add
ret double %mul3
}
; (x + 0.1234 / y) * (x + -0.1234 / y) -> (x + 0.1234 / y) * (x - 0.1234 / y)
; so CSE can simplify it further
define double @lift_sign4(double %x, double %y) nounwind readnone ssp uwtable {
; CHECK-LABEL: @lift_sign4(
%div = fdiv double 1.234000e-01, %y
%add = fadd double %div, %x
%div1 = fdiv double -1.234000e-01, %y
%add2 = fadd double %div1, %x
%mul3 = fmul double %add, %add2
; CHECK-NOT: %div1 = fdiv double -1.234000e-01, %y
; CHECK-NOT: %add2 = fadd double %div1, %x
; CHECK-NOT: %mul3 = fmul double %add, %add2
; CHECK: %add2.repl = fsub double %x, %div
; CHECK: %mul3 = fmul double %add, %add2.repl
ret double %mul3
}