[CodeGenPrepare] sinkCmpExpression - don't sink larger than legal integer comparisons (#166778)

A generic alternative to #166564 - make the assumption that expanding
integer comparisons will be expensive if they are larger than the largest
legal type so avoid sinking if they are also used in the current BB + any phis.

Fixes #166534

Author: RKSimon

llvm/lib/CodeGen/CodeGenPrepare.cpp

@@ -1839,14 +1839,27 @@ bool CodeGenPrepare::unfoldPowerOf2Test(CmpInst *Cmp) {
 /// lose; some adjustment may be wanted there.
 ///
 /// Return true if any changes are made.
-static bool sinkCmpExpression(CmpInst *Cmp, const TargetLowering &TLI) {
+static bool sinkCmpExpression(CmpInst *Cmp, const TargetLowering &TLI,
+                              const DataLayout &DL) {
   if (TLI.hasMultipleConditionRegisters(EVT::getEVT(Cmp->getType())))
     return false;
 
   // Avoid sinking soft-FP comparisons, since this can move them into a loop.
   if (TLI.useSoftFloat() && isa<FCmpInst>(Cmp))
     return false;
 
+  bool UsedInPhiOrCurrentBlock = any_of(Cmp->users(), [Cmp](User *U) {
+    return isa<PHINode>(U) ||
+           cast<Instruction>(U)->getParent() == Cmp->getParent();
+  });
+
+  // Avoid sinking larger than legal integer comparisons unless its ONLY used in
+  // another BB.
+  if (UsedInPhiOrCurrentBlock && Cmp->getOperand(0)->getType()->isIntegerTy() &&
+      Cmp->getOperand(0)->getType()->getScalarSizeInBits() >
+          DL.getLargestLegalIntTypeSizeInBits())
+    return false;
+
   // Only insert a cmp in each block once.
   DenseMap<BasicBlock *, CmpInst *> InsertedCmps;
 
@@ -2224,7 +2237,7 @@ bool CodeGenPrepare::optimizeURem(Instruction *Rem) {
 }
 
 bool CodeGenPrepare::optimizeCmp(CmpInst *Cmp, ModifyDT &ModifiedDT) {
-  if (sinkCmpExpression(Cmp, *TLI))
+  if (sinkCmpExpression(Cmp, *TLI, *DL))
     return true;
 
   if (combineToUAddWithOverflow(Cmp, ModifiedDT))

llvm/test/CodeGen/RISCV/overflow-intrinsics.ll

@@ -232,7 +232,7 @@ define i64 @uaddo3_math_overflow_used(i64 %a, i64 %b, ptr %res) nounwind ssp {
   ret i64 %Q
 }
 
-; TODO? CGP sinks the compare before we have a chance to form the overflow intrinsic.
+; Ensure CGP doesn't sink the compare before we have a chance to form the overflow intrinsic.
 
 define i64 @uaddo4(i64 %a, i64 %b, i1 %c) nounwind ssp {
 ; RV32-LABEL: uaddo4:
@@ -1076,41 +1076,37 @@ define i1 @usubo_ult_cmp_dominates_i64(i64 %x, i64 %y, ptr %p, i1 %cond) {
 ; RV32-NEXT:    .cfi_offset s4, -24
 ; RV32-NEXT:    .cfi_offset s5, -28
 ; RV32-NEXT:    .cfi_offset s6, -32
-; RV32-NEXT:    mv s5, a5
-; RV32-NEXT:    mv s3, a1
+; RV32-NEXT:    mv s1, a5
+; RV32-NEXT:    mv s4, a1
 ; RV32-NEXT:    andi a1, a5, 1
-; RV32-NEXT:    beqz a1, .LBB32_8
+; RV32-NEXT:    beqz a1, .LBB32_6
 ; RV32-NEXT:  # %bb.1: # %t
 ; RV32-NEXT:    mv s0, a4
-; RV32-NEXT:    mv s2, a3
-; RV32-NEXT:    mv s1, a2
-; RV32-NEXT:    mv s4, a0
-; RV32-NEXT:    beq s3, a3, .LBB32_3
+; RV32-NEXT:    mv s3, a3
+; RV32-NEXT:    mv s2, a2
+; RV32-NEXT:    mv s5, a0
+; RV32-NEXT:    beq s4, a3, .LBB32_3
 ; RV32-NEXT:  # %bb.2: # %t
-; RV32-NEXT:    sltu s6, s3, s2
+; RV32-NEXT:    sltu s6, s4, s3
 ; RV32-NEXT:    j .LBB32_4
 ; RV32-NEXT:  .LBB32_3:
-; RV32-NEXT:    sltu s6, s4, s1
+; RV32-NEXT:    sltu s6, s5, s2
 ; RV32-NEXT:  .LBB32_4: # %t
 ; RV32-NEXT:    mv a0, s6
 ; RV32-NEXT:    call call
-; RV32-NEXT:    beqz s6, .LBB32_8
+; RV32-NEXT:    beqz s6, .LBB32_6
 ; RV32-NEXT:  # %bb.5: # %end
-; RV32-NEXT:    sltu a1, s4, s1
-; RV32-NEXT:    mv a0, a1
-; RV32-NEXT:    beq s3, s2, .LBB32_7
-; RV32-NEXT:  # %bb.6: # %end
-; RV32-NEXT:    sltu a0, s3, s2
-; RV32-NEXT:  .LBB32_7: # %end
-; RV32-NEXT:    sub a2, s3, s2
-; RV32-NEXT:    sub a3, s4, s1
-; RV32-NEXT:    sub a2, a2, a1
-; RV32-NEXT:    sw a3, 0(s0)
-; RV32-NEXT:    sw a2, 4(s0)
-; RV32-NEXT:    j .LBB32_9
-; RV32-NEXT:  .LBB32_8: # %f
-; RV32-NEXT:    mv a0, s5
-; RV32-NEXT:  .LBB32_9: # %f
+; RV32-NEXT:    sltu a0, s5, s2
+; RV32-NEXT:    sub a1, s4, s3
+; RV32-NEXT:    sub a2, s5, s2
+; RV32-NEXT:    sub a1, a1, a0
+; RV32-NEXT:    sw a2, 0(s0)
+; RV32-NEXT:    sw a1, 4(s0)
+; RV32-NEXT:    mv a0, s6
+; RV32-NEXT:    j .LBB32_7
+; RV32-NEXT:  .LBB32_6: # %f
+; RV32-NEXT:    mv a0, s1
+; RV32-NEXT:  .LBB32_7: # %f
 ; RV32-NEXT:    lw ra, 28(sp) # 4-byte Folded Reload
 ; RV32-NEXT:    lw s0, 24(sp) # 4-byte Folded Reload
 ; RV32-NEXT:    lw s1, 20(sp) # 4-byte Folded Reload

llvm/test/CodeGen/X86/pr166534.ll

@@ -7,100 +7,64 @@
 define void @pr166534(ptr %pa, ptr %pb, ptr %pc, ptr %pd) {
 ; SSE2-LABEL: pr166534:
 ; SSE2:       # %bb.0: # %entry
-; SSE2-NEXT:    movq (%rdi), %rax
-; SSE2-NEXT:    movq 8(%rdi), %r8
 ; SSE2-NEXT:    movdqu (%rdi), %xmm0
-; SSE2-NEXT:    movq (%rsi), %r9
-; SSE2-NEXT:    movq 8(%rsi), %rdi
 ; SSE2-NEXT:    movdqu (%rsi), %xmm1
 ; SSE2-NEXT:    pcmpeqb %xmm0, %xmm1
 ; SSE2-NEXT:    pmovmskb %xmm1, %esi
-; SSE2-NEXT:    xorl %r10d, %r10d
+; SSE2-NEXT:    xorl %eax, %eax
 ; SSE2-NEXT:    cmpl $65535, %esi # imm = 0xFFFF
-; SSE2-NEXT:    sete %r10b
-; SSE2-NEXT:    orq %r10, (%rdx)
+; SSE2-NEXT:    sete %al
+; SSE2-NEXT:    orq %rax, (%rdx)
 ; SSE2-NEXT:    cmpl $65535, %esi # imm = 0xFFFF
 ; SSE2-NEXT:    jne .LBB0_2
 ; SSE2-NEXT:  # %bb.1: # %if.then
-; SSE2-NEXT:    xorq %r9, %rax
-; SSE2-NEXT:    xorq %rdi, %r8
-; SSE2-NEXT:    xorl %edx, %edx
-; SSE2-NEXT:    orq %rax, %r8
-; SSE2-NEXT:    sete %dl
-; SSE2-NEXT:    orq %rdx, (%rcx)
+; SSE2-NEXT:    orq %rax, (%rcx)
 ; SSE2-NEXT:  .LBB0_2: # %if.end
 ; SSE2-NEXT:    retq
 ;
 ; SSE4-LABEL: pr166534:
 ; SSE4:       # %bb.0: # %entry
-; SSE4-NEXT:    movq (%rdi), %rax
-; SSE4-NEXT:    movq 8(%rdi), %r8
 ; SSE4-NEXT:    movdqu (%rdi), %xmm0
-; SSE4-NEXT:    movq (%rsi), %r9
-; SSE4-NEXT:    movq 8(%rsi), %rdi
 ; SSE4-NEXT:    movdqu (%rsi), %xmm1
 ; SSE4-NEXT:    pxor %xmm0, %xmm1
-; SSE4-NEXT:    xorl %esi, %esi
+; SSE4-NEXT:    xorl %eax, %eax
 ; SSE4-NEXT:    ptest %xmm1, %xmm1
-; SSE4-NEXT:    sete %sil
-; SSE4-NEXT:    orq %rsi, (%rdx)
+; SSE4-NEXT:    sete %al
+; SSE4-NEXT:    orq %rax, (%rdx)
 ; SSE4-NEXT:    ptest %xmm1, %xmm1
 ; SSE4-NEXT:    jne .LBB0_2
 ; SSE4-NEXT:  # %bb.1: # %if.then
-; SSE4-NEXT:    xorq %r9, %rax
-; SSE4-NEXT:    xorq %rdi, %r8
-; SSE4-NEXT:    xorl %edx, %edx
-; SSE4-NEXT:    orq %rax, %r8
-; SSE4-NEXT:    sete %dl
-; SSE4-NEXT:    orq %rdx, (%rcx)
+; SSE4-NEXT:    orq %rax, (%rcx)
 ; SSE4-NEXT:  .LBB0_2: # %if.end
 ; SSE4-NEXT:    retq
 ;
 ; AVX2-LABEL: pr166534:
 ; AVX2:       # %bb.0: # %entry
-; AVX2-NEXT:    movq (%rdi), %rax
-; AVX2-NEXT:    movq 8(%rdi), %r8
 ; AVX2-NEXT:    vmovdqu (%rdi), %xmm0
-; AVX2-NEXT:    movq (%rsi), %rdi
 ; AVX2-NEXT:    vpxor (%rsi), %xmm0, %xmm0
-; AVX2-NEXT:    movq 8(%rsi), %rsi
-; AVX2-NEXT:    xorl %r9d, %r9d
+; AVX2-NEXT:    xorl %eax, %eax
 ; AVX2-NEXT:    vptest %xmm0, %xmm0
-; AVX2-NEXT:    sete %r9b
-; AVX2-NEXT:    orq %r9, (%rdx)
+; AVX2-NEXT:    sete %al
+; AVX2-NEXT:    orq %rax, (%rdx)
 ; AVX2-NEXT:    vptest %xmm0, %xmm0
 ; AVX2-NEXT:    jne .LBB0_2
 ; AVX2-NEXT:  # %bb.1: # %if.then
-; AVX2-NEXT:    xorq %rdi, %rax
-; AVX2-NEXT:    xorq %rsi, %r8
-; AVX2-NEXT:    xorl %edx, %edx
-; AVX2-NEXT:    orq %rax, %r8
-; AVX2-NEXT:    sete %dl
-; AVX2-NEXT:    orq %rdx, (%rcx)
+; AVX2-NEXT:    orq %rax, (%rcx)
 ; AVX2-NEXT:  .LBB0_2: # %if.end
 ; AVX2-NEXT:    retq
 ;
 ; AVX512-LABEL: pr166534:
 ; AVX512:       # %bb.0: # %entry
-; AVX512-NEXT:    movq (%rdi), %rax
-; AVX512-NEXT:    movq 8(%rdi), %r8
 ; AVX512-NEXT:    vmovdqu (%rdi), %xmm0
-; AVX512-NEXT:    movq (%rsi), %r9
-; AVX512-NEXT:    movq 8(%rsi), %rdi
 ; AVX512-NEXT:    vpxor (%rsi), %xmm0, %xmm0
-; AVX512-NEXT:    xorl %esi, %esi
+; AVX512-NEXT:    xorl %eax, %eax
 ; AVX512-NEXT:    vptest %xmm0, %xmm0
-; AVX512-NEXT:    sete %sil
-; AVX512-NEXT:    orq %rsi, (%rdx)
+; AVX512-NEXT:    sete %al
+; AVX512-NEXT:    orq %rax, (%rdx)
 ; AVX512-NEXT:    vptest %xmm0, %xmm0
 ; AVX512-NEXT:    jne .LBB0_2
 ; AVX512-NEXT:  # %bb.1: # %if.then
-; AVX512-NEXT:    xorq %r9, %rax
-; AVX512-NEXT:    xorq %rdi, %r8
-; AVX512-NEXT:    xorl %edx, %edx
-; AVX512-NEXT:    orq %rax, %r8
-; AVX512-NEXT:    sete %dl
-; AVX512-NEXT:    orq %rdx, (%rcx)
+; AVX512-NEXT:    orq %rax, (%rcx)
 ; AVX512-NEXT:  .LBB0_2: # %if.end
 ; AVX512-NEXT:    retq
 entry: