Subzero: Force ebp-based frame when an alloca has a large alignment.

If the alloca alignment exceeds the known ABI stack alignment, the lowering sequence adds an "and esp, xxx" instruction. In this case, the esp adjustment is no longer statically known, so we must force an ebp-based frame. BUG= none R=sehr@google.com Review URL: https://codereview.chromium.org/1426933003 .

Subzero: Force ebp-based frame when an alloca has a large alignment.
8686139f · Jim Stichnoth · 54dbbbaf · 8686139f · 8686139f
Commit 8686139f authored Oct 31, 2015 by Jim Stichnoth
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IceTargetLoweringX86BaseImpl.h src/IceTargetLoweringX86BaseImpl.h +1 -0

alloc.ll tests_lit/llvm2ice_tests/alloc.ll +26 -0

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--- a/src/IceTargetLoweringX86BaseImpl.h
+++ b/src/IceTargetLoweringX86BaseImpl.h
@@ -956,6 +956,7 @@ void TargetX86Base<Machine>::lowerAlloca(const InstAlloca *Inst) {
  uint32_t Alignment =
      std::max(AlignmentParam, Traits::X86_STACK_ALIGNMENT_BYTES);
  if (Alignment > Traits::X86_STACK_ALIGNMENT_BYTES) {
+    IsEbpBasedFrame = true;
    _and(esp, Ctx->getConstantInt32(-Alignment));
  }
  if (const auto *ConstantTotalSize =

--- a/tests_lit/llvm2ice_tests/alloc.ll
+++ b/tests_lit/llvm2ice_tests/alloc.ll
@@ -50,6 +50,8 @@ entry:
  ret void
 }
 ; CHECK-LABEL: fixed_416_align_32
+; CHECK:      push    ebp
+; CHECK-NEXT: mov     ebp,esp
 ; CHECK:      and     esp,0xffffffe0
 ; CHECK:      sub     esp,0x1a0
 ; CHECK:      sub     esp,0x10
@@ -87,6 +89,8 @@ entry:
  ret void
 }
 ; CHECK-LABEL: fixed_351_align_32
+; CHECK:      push    ebp
+; CHECK-NEXT: mov     ebp,esp
 ; CHECK:      and     esp,0xffffffe0
 ; CHECK:      sub     esp,0x160
 ; CHECK:      sub     esp,0x10
@@ -185,6 +189,8 @@ entry:
  ret void
 }
 ; CHECK-LABEL: align1MB
+; CHECK: push ebp
+; CHECK-NEXT: mov ebp,esp
 ; CHECK: and esp,0xfff00000
 ; CHECK: add [[REG:.*]],0xfffff
 ; CHECK: and [[REG]],0xfff00000
@@ -212,6 +218,8 @@ entry:
  ret void
 }
 ; CHECK-LABEL: align512MB
+; CHECK: push ebp
+; CHECK-NEXT: mov ebp,esp
 ; CHECK: and esp,0xe0000000
 ; CHECK: add [[REG:.*]],0x1fffffff
 ; CHECK: and [[REG]],0xe0000000
@@ -241,6 +249,24 @@ entry:
 ; CHECK-LABEL: fixed_no_frameptr
 ; CHECK-NOT:      mov     ebp,esp

+; Test that a simple alloca sequence with at least one large alignment does
+; trigger a frame pointer.
+define internal void @fixed_bigalign_with_frameptr(i32 %arg) {
+entry:
+  %a1 = alloca i8, i32 8, align 4
+  %a2 = alloca i8, i32 12, align 4
+  %a3 = alloca i8, i32 16, align 64
+  %p1 = bitcast i8* %a1 to i32*
+  %p2 = bitcast i8* %a2 to i32*
+  %p3 = bitcast i8* %a3 to i32*
+  store i32 %arg, i32* %p1, align 1
+  store i32 %arg, i32* %p2, align 1
+  store i32 %arg, i32* %p3, align 1
+  ret void
+}
+; CHECK-LABEL: fixed_bigalign_with_frameptr
+; CHECK:      mov     ebp,esp
+
 ; Test that a more complex alloca sequence does trigger a frame pointer.
 define internal void @var_with_frameptr(i32 %arg) {
 entry: