[ARM] Fix offset calculation in ARMBaseRegisterInfo::needsFrameBaseReg

The input offset to needsFrameBaseReg is a negative value below the top of the
stack frame, but when converting to a positive offset from the bottom of the
stack frame this value was negated, causing the final offset to be too large
by twice the input offset's magnitude. Fix that by not negating the offset.

Patch by John Brawn

Differential Revision: http://reviews.llvm.org/D8316

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@232513 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/ARM/ARMBaseRegisterInfo.cpp

@@ -524,7 +524,6 @@ needsFrameBaseReg(MachineInstr *MI, int64_t Offset) const {
   // The incoming offset is relating to the SP at the start of the function,
   // but when we access the local it'll be relative to the SP after local
   // allocation, so adjust our SP-relative offset by that allocation size.
-  Offset = -Offset;
   Offset += MFI->getLocalFrameSize();
   // Assume that we'll have at least some spill slots allocated.
   // FIXME: This is a total SWAG number. We should run some statistics

test/CodeGen/ARM/ssp-data-layout.ll

@@ -21,41 +21,39 @@
 define void @layout_ssp() ssp {
 entry:
 ; Expected stack layout for ssp is
-;  180 large_char          . Group 1, nested arrays, arrays >= ssp-buffer-size
-;  172 struct_large_char   .
-;  168 scalar1             | Everything else
-;  164 scalar2
-;  160 scalar3
-;  156 addr-of
-;  152 small_nonchar (84+68)
+;  176 large_char          . Group 1, nested arrays, arrays >= ssp-buffer-size
+;  168 struct_large_char   .
+;  164 scalar1             | Everything else
+;  160 scalar2
+;  156 scalar3
+;  152 addr-of
+;  148 small_nonchar
 ;  112 large_nonchar
 ;  110 small_char
 ;  108 struct_small_char
 ;   72 struct_large_nonchar
 ;   68 struct_small_nonchar
 
 ; CHECK: layout_ssp:
-; r[[SP]] is used as an offset into the stack later
-; CHECK: add r[[SP:[0-9]+]], sp, #68
 
 ; CHECK: bl get_scalar1
-; CHECK: str r0, [sp, #168]
+; CHECK: str r0, [sp, #164]
 ; CHECK: bl end_scalar1
 
 ; CHECK: bl get_scalar2
-; CHECK: str r0, [sp, #164]
+; CHECK: str r0, [sp, #160]
 ; CHECK: bl end_scalar2
 
 ; CHECK: bl get_scalar3
-; CHECK: str r0, [sp, #160]
+; CHECK: str r0, [sp, #156]
 ; CHECK: bl end_scalar3
 
 ; CHECK: bl get_addrof
-; CHECK: str r0, [sp, #156]
+; CHECK: str r0, [sp, #152]
 ; CHECK: bl end_addrof
 
 ; CHECK: get_small_nonchar
-; CHECK: strh r0, [r[[SP]], #84]
+; CHECK: strh r0, [sp, #148]
 ; CHECK: bl end_small_nonchar
 
 ; CHECK: bl get_large_nonchar
@@ -67,11 +65,11 @@ entry:
 ; CHECK: bl end_small_char
 
 ; CHECK: bl get_large_char
-; CHECK: strb r0, [sp, #180]
+; CHECK: strb r0, [sp, #176]
 ; CHECK: bl end_large_char
 
 ; CHECK: bl get_struct_large_char
-; CHECK: strb r0, [sp, #172]
+; CHECK: strb r0, [sp, #168]
 ; CHECK: bl end_struct_large_char
 
 ; CHECK: bl get_struct_small_char
@@ -83,7 +81,7 @@ entry:
 ; CHECK: bl end_struct_large_nonchar
 
 ; CHECK: bl get_struct_small_nonchar
-; CHECK: strh r0, [r[[SP]]]
+; CHECK: strh r0, [sp, #68]
 ; CHECK: bl end_struct_small_nonchar
   %x = alloca i32, align 4
   %y = alloca i32, align 4
@@ -182,8 +180,6 @@ entry:
 ; 68   scalar3                +
 ;   
 ; CHECK: layout_sspstrong:
-; r[[SP]] is used as an offset into the stack later
-; CHECK: add r[[SP:[0-9]+]], sp, #84
 
 ; CHECK: bl get_scalar1
 ; CHECK: str r0, [sp, #76]
@@ -202,7 +198,7 @@ entry:
 ; CHECK: bl end_addrof
 
 ; CHECK: get_small_nonchar
-; CHECK: strh r0, [r[[SP]], #8]
+; CHECK: strh r0, [sp, #92]
 ; CHECK: bl end_small_nonchar
 
 ; CHECK: bl get_large_nonchar
@@ -230,7 +226,7 @@ entry:
 ; CHECK: bl end_struct_large_nonchar
 
 ; CHECK: bl get_struct_small_nonchar
-; CHECK: strh r0, [r[[SP]]]
+; CHECK: strh r0, [sp, #84]
 ; CHECK: bl end_struct_small_nonchar
   %x = alloca i32, align 4
   %y = alloca i32, align 4
@@ -317,8 +313,6 @@ entry:
 ; Expected stack layout for sspreq is the same as sspstrong
 ;   
 ; CHECK: layout_sspreq:
-; r[[SP]] is used as an offset into the stack later
-; CHECK: add r[[SP:[0-9]+]], sp, #84
 
 ; CHECK: bl get_scalar1
 ; CHECK: str r0, [sp, #76]
@@ -337,7 +331,7 @@ entry:
 ; CHECK: bl end_addrof
 
 ; CHECK: get_small_nonchar
-; CHECK: strh r0, [r[[SP]], #8]
+; CHECK: strh r0, [sp, #92]
 ; CHECK: bl end_small_nonchar
 
 ; CHECK: bl get_large_nonchar
@@ -365,7 +359,7 @@ entry:
 ; CHECK: bl end_struct_large_nonchar
 
 ; CHECK: bl get_struct_small_nonchar
-; CHECK: strh r0, [r[[SP]]]
+; CHECK: strh r0, [sp, #84]
 ; CHECK: bl end_struct_small_nonchar
   %x = alloca i32, align 4
   %y = alloca i32, align 4

test/CodeGen/Thumb/stack-access.ll

@@ -72,3 +72,19 @@ define zeroext i16 @test6() {
   %1 = load i16, i16* %x, align 2
   ret i16 %1
 }
+
+; Accessing the bottom of a large array shouldn't require materializing a base
+define void @test7() {
+  %arr = alloca [200 x i32], align 4
+
+  ; CHECK: movs [[REG:r[0-9]+]], #1
+  ; CHECK: str [[REG]], [sp, #4]
+  %arrayidx = getelementptr inbounds [200 x i32], [200 x i32]* %arr, i32 0, i32 1
+  store i32 1, i32* %arrayidx, align 4
+
+  ; CHECK: str [[REG]], [sp, #16]
+  %arrayidx1 = getelementptr inbounds [200 x i32], [200 x i32]* %arr, i32 0, i32 4
+  store i32 1, i32* %arrayidx1, align 4
+
+  ret void
+}