[llvm] [AMDGPU] Implement IR variant of isFMAFasterThanFMulAndFAdd (PR #121465)

[Matt Arsenault via llvm-commits]

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@@ -0,0 +1,185 @@
+; NOTE: Assertions have been autogenerated by utils/update_test_checks.py UTC_ARGS: --version 5
+; RUN: opt -S -passes=simplifycfg -verify-machineinstrs -hoist-common-insts=true -mtriple=amdgcn-- -mcpu=gfx1030 -fp-contract=fast < %s | FileCheck -check-prefix=GFX -check-prefix=GFX-FP-CONTRACT %s
+; RUN: opt -S -passes=simplifycfg -verify-machineinstrs -hoist-common-insts=true -mtriple=amdgcn-- -mcpu=gfx1030 -enable-unsafe-fp-math --denormal-fp-math=ieee < %s | FileCheck -check-prefix=GFX -check-prefix=GFX-UNSAFE-FP-IEEE %s
+; RUN: opt -S -passes=simplifycfg -verify-machineinstrs -hoist-common-insts=true -mtriple=amdgcn-- -mcpu=gfx1030 -enable-unsafe-fp-math --denormal-fp-math=preserve-sign < %s | FileCheck -check-prefix=GFX -check-prefix=GFX-UNSAFE-FP-PRESERVE %s
+
+define double @_branch(ptr dereferenceable(8) %x, ptr dereferenceable(8) %y, ptr dereferenceable(8) %a) #0 {
+; GFX-LABEL: define double @_branch(
+; GFX-SAME: ptr dereferenceable(8) [[X:%.*]], ptr dereferenceable(8) [[Y:%.*]], ptr dereferenceable(8) [[A:%.*]]) #[[ATTR0:[0-9]+]] {
+; GFX-NEXT:  [[ENTRY:.*:]]
+; GFX-NEXT:    [[TMP0:%.*]] = load double, ptr [[Y]], align 8
+; GFX-NEXT:    [[CMP:%.*]] = fcmp oeq double [[TMP0]], 0.000000e+00
+; GFX-NEXT:    [[TMP1:%.*]] = load double, ptr [[X]], align 8
+; GFX-NEXT:    [[TMP2:%.*]] = load double, ptr [[A]], align 8
+; GFX-NEXT:    br i1 [[CMP]], label %[[IF_THEN:.*]], label %[[IF_ELSE:.*]]
+; GFX:       [[COMMON_RET:.*]]:
+; GFX-NEXT:    [[COMMON_RET_OP:%.*]] = phi double [ [[MUL:%.*]], %[[IF_THEN]] ], [ [[SUB:%.*]], %[[IF_ELSE]] ]
+; GFX-NEXT:    ret double [[COMMON_RET_OP]]
+; GFX:       [[IF_THEN]]:
+; GFX-NEXT:    [[MUL]] = fmul fast double [[TMP1]], [[TMP2]]
+; GFX-NEXT:    [[ADD:%.*]] = fadd fast double 1.000000e+00, [[MUL]]
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arsenm wrote:

Reduce to minimal flags (contract)

https://github.com/llvm/llvm-project/pull/121465