[PATCH] D45572: [X86] Replace action Promote with Custom for operation ISD::SINT_TO_FP

[Vyacheslav via Phabricator via llvm-commits]

vrybalov created this revision.
Herald added a subscriber: llvm-commits.

If attribute "use-soft-float"="true" is set then X86ISelLowering.cpp sets                                                                                                                                                                    'Promote' action for ISD::SINT_TO_FP operation on type i32.

                                                                                                                                                               But 'Promote' action is not proper in this case since lib function                                                                                                                                                                            __floatsidf is available for casting from signed int to float type.                                                                                                                                                                         Thus Custom action is more suitable here.                                                                                                                                                                                                
                                                                                                                                                               If function attribute "use-soft-float"="true" is set then infinite looping                                                                                                                                                                   can happen in DAG combining, function visitSINT_TO_FP() replaces SINT_TO_FP                                                                                                                                                                  node with UINT_TO_FP node and function combineUIntToFP() replace vice versa in cycle.                                                                                                                                                        The fix prevents it.


Repository:
  rL LLVM

https://reviews.llvm.org/D45572

Files:
  lib/Target/X86/X86ISelLowering.cpp
  test/CodeGen/X86/sitofp.ll


Index: test/CodeGen/X86/sitofp.ll
===================================================================
--- /dev/null
+++ test/CodeGen/X86/sitofp.ll
@@ -0,0 +1,17 @@
+; RUN: llc < %s
+
+target triple = "i386-unknown-linux-gnu"
+
+define void @foo() #0 {
+entry:
+  %a = alloca i16, align 2
+  %b = alloca double, align 4
+  %0 = load i16, i16* %a, align 2
+  %conv = zext i16 %0 to i32
+  %conv1 = sitofp i32 %conv to double
+  %add = fadd double %conv1, 0.000000e+00
+  store double %add, double* %b, align 4
+  ret void
+}
+
+attributes #0 = { "use-soft-float"="true" }
Index: lib/Target/X86/X86ISelLowering.cpp
===================================================================
--- lib/Target/X86/X86ISelLowering.cpp
+++ lib/Target/X86/X86ISelLowering.cpp
@@ -235,7 +235,7 @@
     }
   } else {
     setOperationAction(ISD::SINT_TO_FP     , MVT::i16  , Promote);
-    setOperationAction(ISD::SINT_TO_FP     , MVT::i32  , Promote);
+    setOperationAction(ISD::SINT_TO_FP     , MVT::i32  , Custom);
   }
 
   // Promote i1/i8 FP_TO_SINT to larger FP_TO_SINTS's, as X86 doesn't have


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