Allow speculating llvm.sqrt, fma and fmuladd
This doesn't set errno, so this should be OK.
Also update the documentation to explicitly state
that errno are not set.
llvm-svn: 200501
diff --git a/llvm/docs/LangRef.rst b/llvm/docs/LangRef.rst
index d1eaee1..62ce112 100644
--- a/llvm/docs/LangRef.rst
+++ b/llvm/docs/LangRef.rst
@@ -7490,7 +7490,7 @@
""""""""""
This function returns the same values as the libm ``fma`` functions
-would.
+would, and does not set errno.
'``llvm.fabs.*``' Intrinsic
^^^^^^^^^^^^^^^^^^^^^^^^^^^
@@ -8298,7 +8298,8 @@
not be performed between the multiplication and addition steps if the
code generator fuses the operations. Fusion is not guaranteed, even if
the target platform supports it. If a fused multiply-add is required the
-corresponding llvm.fma.\* intrinsic function should be used instead.
+corresponding llvm.fma.\* intrinsic function should be used
+instead. This never sets errno, just as '``llvm.fma.*``'.
Examples:
"""""""""
diff --git a/llvm/lib/Analysis/ValueTracking.cpp b/llvm/lib/Analysis/ValueTracking.cpp
index 1e423c4..5ebb613 100644
--- a/llvm/lib/Analysis/ValueTracking.cpp
+++ b/llvm/lib/Analysis/ValueTracking.cpp
@@ -2036,6 +2036,12 @@
case Intrinsic::umul_with_overflow:
case Intrinsic::usub_with_overflow:
return true;
+ // Sqrt should be OK, since the llvm sqrt intrinsic isn't defined to set
+ // errno like libm sqrt would.
+ case Intrinsic::sqrt:
+ case Intrinsic::fma:
+ case Intrinsic::fmuladd:
+ return true;
// TODO: some fp intrinsics are marked as having the same error handling
// as libm. They're safe to speculate when they won't error.
// TODO: are convert_{from,to}_fp16 safe?
diff --git a/llvm/test/Transforms/SimplifyCFG/speculate-math.ll b/llvm/test/Transforms/SimplifyCFG/speculate-math.ll
new file mode 100644
index 0000000..fa7976d
--- /dev/null
+++ b/llvm/test/Transforms/SimplifyCFG/speculate-math.ll
@@ -0,0 +1,58 @@
+; RUN: opt -S -simplifycfg -phi-node-folding-threshold=2 < %s | FileCheck %s
+
+declare float @llvm.sqrt.f32(float) nounwind readonly
+declare float @llvm.fma.f32(float, float, float) nounwind readonly
+declare float @llvm.fmuladd.f32(float, float, float) nounwind readonly
+
+; CHECK-LABEL: @sqrt_test(
+; CHECK: select
+define void @sqrt_test(float addrspace(1)* noalias nocapture %out, float %a) nounwind {
+entry:
+ %cmp.i = fcmp olt float %a, 0.000000e+00
+ br i1 %cmp.i, label %test_sqrt.exit, label %cond.else.i
+
+cond.else.i: ; preds = %entry
+ %0 = tail call float @llvm.sqrt.f32(float %a) nounwind readnone
+ br label %test_sqrt.exit
+
+test_sqrt.exit: ; preds = %cond.else.i, %entry
+ %cond.i = phi float [ %0, %cond.else.i ], [ 0x7FF8000000000000, %entry ]
+ store float %cond.i, float addrspace(1)* %out, align 4
+ ret void
+}
+
+
+; CHECK-LABEL: @fma_test(
+; CHECK: select
+define void @fma_test(float addrspace(1)* noalias nocapture %out, float %a, float %b, float %c) nounwind {
+entry:
+ %cmp.i = fcmp olt float %a, 0.000000e+00
+ br i1 %cmp.i, label %test_fma.exit, label %cond.else.i
+
+cond.else.i: ; preds = %entry
+ %0 = tail call float @llvm.fma.f32(float %a, float %b, float %c) nounwind readnone
+ br label %test_fma.exit
+
+test_fma.exit: ; preds = %cond.else.i, %entry
+ %cond.i = phi float [ %0, %cond.else.i ], [ 0x7FF8000000000000, %entry ]
+ store float %cond.i, float addrspace(1)* %out, align 4
+ ret void
+}
+
+; CHECK-LABEL: @fmuladd_test(
+; CHECK: select
+define void @fmuladd_test(float addrspace(1)* noalias nocapture %out, float %a, float %b, float %c) nounwind {
+entry:
+ %cmp.i = fcmp olt float %a, 0.000000e+00
+ br i1 %cmp.i, label %test_fmuladd.exit, label %cond.else.i
+
+cond.else.i: ; preds = %entry
+ %0 = tail call float @llvm.fmuladd.f32(float %a, float %b, float %c) nounwind readnone
+ br label %test_fmuladd.exit
+
+test_fmuladd.exit: ; preds = %cond.else.i, %entry
+ %cond.i = phi float [ %0, %cond.else.i ], [ 0x7FF8000000000000, %entry ]
+ store float %cond.i, float addrspace(1)* %out, align 4
+ ret void
+}
+