[PATCH] [SPARC] Fix BooleanContents, so that select of a trunc doesn't eliminate the trunc.

[James Y Knight]

http://reviews.llvm.org/D10871

Files:
  lib/Target/Sparc/SparcISelLowering.cpp
  test/CodeGen/SPARC/select-mask.ll

Index: lib/Target/Sparc/SparcISelLowering.cpp
===================================================================
--- lib/Target/Sparc/SparcISelLowering.cpp
+++ lib/Target/Sparc/SparcISelLowering.cpp
@@ -1370,6 +1370,15 @@
 SparcTargetLowering::SparcTargetLowering(TargetMachine &TM,
                                          const SparcSubtarget &STI)
     : TargetLowering(TM), Subtarget(&STI) {
+
+  // Instruction which use registers as conditionals examine all the
+  // bits (as does the pseudo SELECT_CC expansion). I don't think it
+  // matters much whether it's ZeroOrOneBooleanContent, or
+  // ZeroOrNegativeOneBooleanContent, so, arbitrarily choose the
+  // former.
+  setBooleanContents(ZeroOrOneBooleanContent);
+  setBooleanVectorContents(ZeroOrOneBooleanContent);
+
   // Set up the register classes.
   addRegisterClass(MVT::i32, &SP::IntRegsRegClass);
   addRegisterClass(MVT::f32, &SP::FPRegsRegClass);
Index: test/CodeGen/SPARC/select-mask.ll
===================================================================
--- /dev/null
+++ test/CodeGen/SPARC/select-mask.ll
@@ -0,0 +1,17 @@
+; RUN: llc -march=sparc < %s
+
+;; getBooleanContents on Sparc used to claim that no bits mattered
+;; other than the first for SELECT. Thus, the 'trunc' got eliminated
+;; as redundant. But, cmp does NOT ignore the other bits!
+
+; CHECK-LABEL select_mask:
+; CHECK: ldub [%o0], [[R:%[goli][0-7]]]
+; CHECK: and [[R]], 1, [[V:%[goli][0-7]]]
+; CHECK: cmp [[V]], 0
+define i32 @select_mask(i8* %this) {
+entry:
+  %bf.load2 = load i8, i8* %this, align 4
+  %bf.cast5 = trunc i8 %bf.load2 to i1
+  %cond = select i1 %bf.cast5, i32 2, i32 0
+  ret i32 %cond
+}

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