Revert "[X86] Promote cttz_i32(x) -> cttz_i64((i64)x | (1 << 32))" (l…

…lvm#103030) Reverts llvm#102900 - missed a analysis cost model test change
SpencerAbson · Aug 13, 2024 · 346a1c5 · 346a1c5
1 parent f9b15a9
commit 346a1c5
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Showing 5 changed files with 240 additions and 154 deletions.
diff --git a/llvm/lib/Target/X86/X86ISelLowering.cpp b/llvm/lib/Target/X86/X86ISelLowering.cpp
@@ -412,7 +412,6 @@ X86TargetLowering::X86TargetLowering(const X86TargetMachine &TM,
     setOperationAction(ISD::CTTZ           , MVT::i32  , Custom);
     setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i32  , Legal);
     if (Subtarget.is64Bit()) {
-      setOperationPromotedToType(ISD::CTTZ , MVT::i32, MVT::i64);
       setOperationAction(ISD::CTTZ         , MVT::i64  , Custom);
       setOperationAction(ISD::CTTZ_ZERO_UNDEF, MVT::i64, Legal);
     }
@@ -3238,10 +3237,9 @@ bool X86TargetLowering::shouldFormOverflowOp(unsigned Opcode, EVT VT,
 }
 
 bool X86TargetLowering::isCheapToSpeculateCttz(Type *Ty) const {
-  // Speculate cttz only if we can directly use TZCNT or can promote to i32/i64.
+  // Speculate cttz only if we can directly use TZCNT or can promote to i32.
   return Subtarget.hasBMI() ||
-         (!Ty->isVectorTy() &&
-          Ty->getScalarSizeInBits() < (Subtarget.is64Bit() ? 64u : 32u));
+         (!Ty->isVectorTy() && Ty->getScalarSizeInBits() < 32);
 }
 
 bool X86TargetLowering::isCheapToSpeculateCtlz(Type *Ty) const {

diff --git a/llvm/test/CodeGen/X86/cttz.ll b/llvm/test/CodeGen/X86/cttz.ll
@@ -317,11 +317,13 @@ define i32 @cttz_i32_zero_test(i32 %n) {
 ;
 ; X64-LABEL: cttz_i32_zero_test:
 ; X64:       # %bb.0:
-; X64-NEXT:    # kill: def $edi killed $edi def $rdi
-; X64-NEXT:    movabsq $4294967296, %rax # imm = 0x100000000
-; X64-NEXT:    orq %rdi, %rax
-; X64-NEXT:    rep bsfq %rax, %rax
-; X64-NEXT:    # kill: def $eax killed $eax killed $rax
+; X64-NEXT:    testl %edi, %edi
+; X64-NEXT:    je .LBB6_1
+; X64-NEXT:  # %bb.2: # %cond.false
+; X64-NEXT:    rep bsfl %edi, %eax
+; X64-NEXT:    retq
+; X64-NEXT:  .LBB6_1:
+; X64-NEXT:    movl $32, %eax
 ; X64-NEXT:    retq
 ;
 ; X86-CLZ-LABEL: cttz_i32_zero_test: