[llvm] r305734 - [CGP, PowerPC] try to constant fold before creating loads for memcmp expansion

[Sanjay Patel via llvm-commits]

Author: spatel
Date: Mon Jun 19 14:48:35 2017
New Revision: 305734

URL: http://llvm.org/viewvc/llvm-project?rev=305734&view=rev
Log:
[CGP, PowerPC] try to constant fold before creating loads for memcmp expansion

This is the last step needed to avoid regressions for x86 before we flip the switch to allow 
expansion of the smallest set of memcpy() via CGP. The DAG version checks for constant strings, 
so we need to do that here too.

FWIW, the 2 constant test is not handled by LibCallSimplifier::optimizeMemCmp() because that 
code is limited to 8-bit constant arrays. LibCallSimplifier will also fail to optimize some 1 
constant tests because its alignment requirements are too strict (shouldn't require alignment 
for a constant operand).

Differential Revision: https://reviews.llvm.org/D34071

Modified:
    llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
    llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll

Modified: llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp?rev=305734&r1=305733&r2=305734&view=diff
==============================================================================
--- llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp (original)
+++ llvm/trunk/lib/CodeGen/CodeGenPrepare.cpp Mon Jun 19 14:48:35 2017
@@ -1851,9 +1851,19 @@ Value *MemCmpExpansion::getCompareLoadPa
                                   ConstantInt::get(LoadSizeType, GEPIndex));
     }
 
-    // Load LoadSizeType from the base address.
-    Value *LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
-    Value *LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
+    // Get a constant or load a value for each source address.
+    Value *LoadSrc1 = nullptr;
+    if (auto *Source1C = dyn_cast<Constant>(Source1))
+      LoadSrc1 = ConstantFoldLoadFromConstPtr(Source1C, LoadSizeType, DL);
+    if (!LoadSrc1)
+      LoadSrc1 = Builder.CreateLoad(LoadSizeType, Source1);
+
+    Value *LoadSrc2 = nullptr;
+    if (auto *Source2C = dyn_cast<Constant>(Source2))
+      LoadSrc2 = ConstantFoldLoadFromConstPtr(Source2C, LoadSizeType, DL);
+    if (!LoadSrc2)
+      LoadSrc2 = Builder.CreateLoad(LoadSizeType, Source2);
+
     if (NumLoads != 1) {
       if (LoadSizeType != MaxLoadType) {
         LoadSrc1 = Builder.CreateZExtOrTrunc(LoadSrc1, MaxLoadType);

Modified: llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll?rev=305734&r1=305733&r2=305734&view=diff
==============================================================================
--- llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll (original)
+++ llvm/trunk/test/CodeGen/PowerPC/memCmpUsedInZeroEqualityComparison.ll Mon Jun 19 14:48:35 2017
@@ -168,26 +168,8 @@ define signext i32 @zeroEqualityTest05()
 ; Validate with memcmp()?:
 define signext i32 @equalityFoldTwoConstants() {
 ; CHECK-LABEL: equalityFoldTwoConstants:
-; CHECK:       # BB#0: # %loadbb
-; CHECK-NEXT:    addis 3, 2, .LzeroEqualityTest04.buffer1 at toc@ha
-; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer2 at toc@ha
-; CHECK-NEXT:    ld 3, .LzeroEqualityTest04.buffer1 at toc@l(3)
-; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer2 at toc@l(4)
-; CHECK-NEXT:    cmpld 3, 4
-; CHECK-NEXT:    bne 0, .LBB5_2
-; CHECK-NEXT:  # BB#1: # %loadbb1
-; CHECK-NEXT:    addis 3, 2, .LzeroEqualityTest04.buffer1 at toc@ha+8
-; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer2 at toc@ha+8
-; CHECK-NEXT:    ld 3, .LzeroEqualityTest04.buffer1 at toc@l+8(3)
-; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer2 at toc@l+8(4)
-; CHECK-NEXT:    cmpld 3, 4
-; CHECK-NEXT:    li 3, 0
-; CHECK-NEXT:    beq 0, .LBB5_3
-; CHECK-NEXT:  .LBB5_2: # %res_block
+; CHECK:       # BB#0: # %endblock
 ; CHECK-NEXT:    li 3, 1
-; CHECK-NEXT:  .LBB5_3: # %endblock
-; CHECK-NEXT:    cntlzw 3, 3
-; CHECK-NEXT:    srwi 3, 3, 5
 ; CHECK-NEXT:    blr
   %call = tail call signext i32 @memcmp(i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer1 to i8*), i8* bitcast ([15 x i32]* @zeroEqualityTest04.buffer2 to i8*), i64 16)
   %not.tobool = icmp eq i32 %call, 0
@@ -198,16 +180,17 @@ define signext i32 @equalityFoldTwoConst
 define signext i32 @equalityFoldOneConstant(i8* %X) {
 ; CHECK-LABEL: equalityFoldOneConstant:
 ; CHECK:       # BB#0: # %loadbb
-; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer1 at toc@ha
+; CHECK-NEXT:    li 4, 1
 ; CHECK-NEXT:    ld 5, 0(3)
-; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer1 at toc@l(4)
-; CHECK-NEXT:    cmpld 4, 5
+; CHECK-NEXT:    sldi 4, 4, 32
+; CHECK-NEXT:    cmpld 5, 4
 ; CHECK-NEXT:    bne 0, .LBB6_2
 ; CHECK-NEXT:  # BB#1: # %loadbb1
-; CHECK-NEXT:    addis 4, 2, .LzeroEqualityTest04.buffer1 at toc@ha+8
+; CHECK-NEXT:    li 4, 3
 ; CHECK-NEXT:    ld 3, 8(3)
-; CHECK-NEXT:    ld 4, .LzeroEqualityTest04.buffer1 at toc@l+8(4)
-; CHECK-NEXT:    cmpld 4, 3
+; CHECK-NEXT:    sldi 4, 4, 32
+; CHECK-NEXT:    ori 4, 4, 2
+; CHECK-NEXT:    cmpld 3, 4
 ; CHECK-NEXT:    li 3, 0
 ; CHECK-NEXT:    beq 0, .LBB6_3
 ; CHECK-NEXT:  .LBB6_2: # %res_block