[DAGCombine] Fix for PR37563

While searching for loads to be narrowed, equal sized loads were not
added to the list, resulting in anyext loads not being converted to
zext loads.

https://bugs.llvm.org/show_bug.cgi?id=35763

Differential Revision: https://reviews.llvm.org/D41628

llvm-svn: 321862

3 files changed, 21 insertions, 14 deletions

diff --git a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
index 25ae71c57cb..1fcb010eac5 100644
--- a/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
+++ b/llvm/lib/CodeGen/SelectionDAG/DAGCombiner.cpp
@@ -3842,9 +3842,16 @@ bool DAGCombiner::SearchForAndLoads(SDNode *N,
       EVT ExtVT;
       if (isAndLoadExtLoad(Mask, Load, Load->getValueType(0), ExtVT) &&
           isLegalNarrowLoad(Load, ISD::ZEXTLOAD, ExtVT)) {
-        // Only add this load if we can make it more narrow.
-        if (ExtVT.bitsLT(Load->getMemoryVT()))
+
+        // ZEXTLOAD is already small enough.
+        if (Load->getExtensionType() == ISD::ZEXTLOAD &&
+            ExtVT.bitsGE(Load->getMemoryVT()))
+          continue;
+
+        // Use LE to convert equal sized loads to zext.
+        if (ExtVT.bitsLE(Load->getMemoryVT()))
           Loads.insert(Load);
+
         continue;
       }
       return false;
@@ -3899,11 +3906,13 @@ bool DAGCombiner::BackwardsPropagateMask(SDNode *N, SelectionDAG &DAG) {
     if (Loads.size() == 0)
       return false;
 
+    DEBUG(dbgs() << "Backwards propagate AND: "; N->dump());
     SDValue MaskOp = N->getOperand(1);
 
     // If it exists, fixup the single node we allow in the tree that needs
     // masking.
     if (FixupNode) {
+      DEBUG(dbgs() << "First, need to fix up: "; FixupNode->dump());
       SDValue And = DAG.getNode(ISD::AND, SDLoc(FixupNode),
                                 FixupNode->getValueType(0),
                                 SDValue(FixupNode, 0), MaskOp);
@@ -3922,6 +3931,7 @@ bool DAGCombiner::BackwardsPropagateMask(SDNode *N, SelectionDAG &DAG) {
 
     // Create narrow loads.
     for (auto *Load : Loads) {
+      DEBUG(dbgs() << "Propagate AND back to: "; Load->dump());
       SDValue And = DAG.getNode(ISD::AND, SDLoc(Load), Load->getValueType(0),
                                 SDValue(Load, 0), MaskOp);
       DAG.ReplaceAllUsesOfValueWith(SDValue(Load, 0), And);
diff --git a/llvm/test/CodeGen/ARM/and-load-combine.ll b/llvm/test/CodeGen/ARM/and-load-combine.ll
index 2b92778f469..69b00ed4853 100644
--- a/llvm/test/CodeGen/ARM/and-load-combine.ll
+++ b/llvm/test/CodeGen/ARM/and-load-combine.ll
@@ -852,8 +852,7 @@ define arm_aapcscc i1 @test6(i8* %x, i8 %y, i8 %z) {
 ; ARM:       @ %bb.0: @ %entry
 ; ARM-NEXT:    ldrb r0, [r0]
 ; ARM-NEXT:    uxtb r2, r2
-; ARM-NEXT:    and r0, r0, r1
-; ARM-NEXT:    uxtb r1, r0
+; ARM-NEXT:    and r1, r0, r1
 ; ARM-NEXT:    mov r0, #0
 ; ARM-NEXT:    cmp r1, r2
 ; ARM-NEXT:    movweq r0, #1
@@ -863,8 +862,7 @@ define arm_aapcscc i1 @test6(i8* %x, i8 %y, i8 %z) {
 ; ARMEB:       @ %bb.0: @ %entry
 ; ARMEB-NEXT:    ldrb r0, [r0]
 ; ARMEB-NEXT:    uxtb r2, r2
-; ARMEB-NEXT:    and r0, r0, r1
-; ARMEB-NEXT:    uxtb r1, r0
+; ARMEB-NEXT:    and r1, r0, r1
 ; ARMEB-NEXT:    mov r0, #0
 ; ARMEB-NEXT:    cmp r1, r2
 ; ARMEB-NEXT:    movweq r0, #1
@@ -872,9 +870,8 @@ define arm_aapcscc i1 @test6(i8* %x, i8 %y, i8 %z) {
 ;
 ; THUMB1-LABEL: test6:
 ; THUMB1:       @ %bb.0: @ %entry
-; THUMB1-NEXT:    ldrb r0, [r0]
-; THUMB1-NEXT:    ands r0, r1
-; THUMB1-NEXT:    uxtb r3, r0
+; THUMB1-NEXT:    ldrb r3, [r0]
+; THUMB1-NEXT:    ands r3, r1
 ; THUMB1-NEXT:    uxtb r2, r2
 ; THUMB1-NEXT:    movs r0, #1
 ; THUMB1-NEXT:    movs r1, #0
@@ -889,8 +886,7 @@ define arm_aapcscc i1 @test6(i8* %x, i8 %y, i8 %z) {
 ; THUMB2:       @ %bb.0: @ %entry
 ; THUMB2-NEXT:    ldrb r0, [r0]
 ; THUMB2-NEXT:    uxtb r2, r2
-; THUMB2-NEXT:    ands r0, r1
-; THUMB2-NEXT:    uxtb r1, r0
+; THUMB2-NEXT:    ands r1, r0
 ; THUMB2-NEXT:    movs r0, #0
 ; THUMB2-NEXT:    cmp r1, r2
 ; THUMB2-NEXT:    it eq
diff --git a/llvm/test/CodeGen/X86/pr37563.ll b/llvm/test/CodeGen/X86/pr37563.ll
index f909eca9036..934902d8e0d 100644
--- a/llvm/test/CodeGen/X86/pr37563.ll
+++ b/llvm/test/CodeGen/X86/pr37563.ll
@@ -10,9 +10,10 @@
 define void @PR35763() {
 ; CHECK-LABEL: PR35763:
 ; CHECK:       # %bb.0: # %entry
-; CHECK-NEXT:    movzwl z+{{.*}}(%rip), %eax
-; CHECK-NEXT:    orl {{.*}}(%rip), %eax
-; CHECK-NEXT:    movq %rax, {{.*}}(%rip)
+; CHECK-NEXT:    movzwl {{.*}}(%rip), %eax
+; CHECK-NEXT:    movzwl z+{{.*}}(%rip), %ecx
+; CHECK-NEXT:    orl %eax, %ecx
+; CHECK-NEXT:    movq %rcx, {{.*}}(%rip)
 ; CHECK-NEXT:    movl z+{{.*}}(%rip), %eax
 ; CHECK-NEXT:    movzbl z+{{.*}}(%rip), %ecx
 ; CHECK-NEXT:    shlq $32, %rcx