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 .

diff --git a/src/IceTargetLoweringX86BaseImpl.h b/src/IceTargetLoweringX86BaseImpl.h
index 1ad9b29..b6b54e3 100644 (file)
--- 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 =

diff --git a/tests_lit/llvm2ice_tests/alloc.ll b/tests_lit/llvm2ice_tests/alloc.ll
index 49faa7e..53e1842 100644 (file)
--- 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: