[X86] Teach X86TargetLowering::targetShrinkDemandedConstant to set non-demanded bits if it helps created an and mask that can be matched as a zero extend.

I had to modify the bswap recognition to allow unshrunk masks to make this work.

Fixes PR36689.

Differential Revision: https://reviews.llvm.org/D44442

llvm-svn: 327530

3 files changed, 18 insertions, 11 deletions

diff --git a/llvm/test/CodeGen/X86/pr12360.ll b/llvm/test/CodeGen/X86/pr12360.ll
index 73dd4966dbb..6ffa2fc5de6 100644
--- a/llvm/test/CodeGen/X86/pr12360.ll
+++ b/llvm/test/CodeGen/X86/pr12360.ll
@@ -45,9 +45,9 @@ entry:
 define zeroext i1 @f4(i32 %x) {
 ; CHECK-LABEL: f4:
 ; CHECK:       ## %bb.0: ## %entry
-; CHECK-NEXT:    shrl $15, %edi
-; CHECK-NEXT:    andl $1, %edi
-; CHECK-NEXT:    movl %edi, %eax
+; CHECK-NEXT:    movzwl %di, %eax
+; CHECK-NEXT:    shrl $15, %eax
+; CHECK-NEXT:    ## kill: def $al killed $al killed $eax
 ; CHECK-NEXT:    retq
 
 entry:
diff --git a/llvm/test/CodeGen/X86/pr32284.ll b/llvm/test/CodeGen/X86/pr32284.ll
index 62e7a66a0f1..44367cbdaa8 100644
--- a/llvm/test/CodeGen/X86/pr32284.ll
+++ b/llvm/test/CodeGen/X86/pr32284.ll
@@ -514,8 +514,6 @@ define void @f3() #0 {
 ; 686-O0-NEXT:    movl %ecx, %edi
 ; 686-O0-NEXT:    xorl %esi, %edi
 ; 686-O0-NEXT:    andl %edi, %eax
-; 686-O0-NEXT:    movb %al, %dl
-; 686-O0-NEXT:    movzbl %dl, %eax
 ; 686-O0-NEXT:    orl %eax, %ecx
 ; 686-O0-NEXT:    movl %ecx, (%esp)
 ; 686-O0-NEXT:    movl $0, {{[0-9]+}}(%esp)
@@ -545,9 +543,8 @@ define void @f3() #0 {
 ; 686-NEXT:    movl var_16, %edx
 ; 686-NEXT:    xorl %ecx, %edx
 ; 686-NEXT:    andl %eax, %edx
-; 686-NEXT:    movzbl %dl, %eax
-; 686-NEXT:    orl %ecx, %eax
-; 686-NEXT:    movl %eax, (%esp)
+; 686-NEXT:    orl %ecx, %edx
+; 686-NEXT:    movl %edx, (%esp)
 ; 686-NEXT:    movl $0, {{[0-9]+}}(%esp)
 ; 686-NEXT:    movl %ecx, var_46
 ; 686-NEXT:    movl %ebp, %esp
diff --git a/llvm/test/CodeGen/X86/zext-demanded.ll b/llvm/test/CodeGen/X86/zext-demanded.ll
index c292b0bc1dc..acfe8f42df9 100644
--- a/llvm/test/CodeGen/X86/zext-demanded.ll
+++ b/llvm/test/CodeGen/X86/zext-demanded.ll
@@ -76,9 +76,8 @@ define i32 @test6(i32 %x) {
 define i32 @test7(i32 %x) {
 ; CHECK-LABEL: test7:
 ; CHECK:       # %bb.0:
-; CHECK-NEXT:    # kill: def $edi killed $edi def $rdi
-; CHECK-NEXT:    andl $65534, %edi # imm = 0xFFFE
-; CHECK-NEXT:    leal 1(%rdi), %eax
+; CHECK-NEXT:    orl $1, %edi
+; CHECK-NEXT:    movzwl %di, %eax
 ; CHECK-NEXT:    retq
   %y = and i32 %x, 65534
   %z = or i32 %y, 1
@@ -138,3 +137,14 @@ define i64 @mul_neg_one(i64 %x) {
   ret i64 %r
 }
 
+define i32 @PR36689(i32*) {
+; CHECK-LABEL: PR36689:
+; CHECK:       # %bb.0:
+; CHECK-NEXT:    movzwl (%rdi), %eax
+; CHECK-NEXT:    orl $255, %eax
+; CHECK-NEXT:    retq
+  %2 = load i32, i32* %0
+  %3 = and i32 %2, 65280
+  %4 = or i32 %3, 255
+  ret i32 %4
+}