[PATCH] D32858: [ARM] Mark LEApcrel instructions as isAsCheapAsAMove

[John Brawn via Phabricator via llvm-commits]

john.brawn created this revision.
Herald added subscribers: rengolin, aemerson.

Doing this means that if an LEApcrel is used in two places we will rematerialize instead of generating two MOVs. This is particularly useful for printfs using the same format string, where we want to generate an address into a register that's going to get corrupted by the call.


Repository:
  rL LLVM

https://reviews.llvm.org/D32858

Files:
  lib/Target/ARM/ARMInstrInfo.td
  lib/Target/ARM/ARMInstrThumb.td
  lib/Target/ARM/ARMInstrThumb2.td
  test/CodeGen/ARM/adr-remat.ll
  test/CodeGen/ARM/align-sp-adjustment.ll


Index: test/CodeGen/ARM/align-sp-adjustment.ll
===================================================================
--- test/CodeGen/ARM/align-sp-adjustment.ll
+++ test/CodeGen/ARM/align-sp-adjustment.ll
@@ -1,6 +1,10 @@
 ; RUN: llc -mtriple=thumbv7 -o - %s | FileCheck %s
 
-; CHECK: [sp, #2120]
+; p5 will have been pushed to the stack. Check that it's correctly aligned by
+; looking at the offset of the instruction that loads it. Note that this is
+; very fragile and this test may need to be updated if we happen to spill more
+; or less to the stack.
+; CHECK: ldr{{(.w)?}} r{{[0-9]+}}, [sp, #2104]
 
 %struct.struct_2 = type { [172 x %struct.struct_1] }
 %struct.struct_1 = type { i32, i32, i32 }
Index: test/CodeGen/ARM/adr-remat.ll
===================================================================
--- /dev/null
+++ test/CodeGen/ARM/adr-remat.ll
@@ -0,0 +1,25 @@
+; RUN: llc -mtriple=armv7a   %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv7m %s -o - | FileCheck %s
+; RUN: llc -mtriple=thumbv6m %s -o - | FileCheck %s
+
+ at str.1 = private unnamed_addr constant [58 x i8] c"+-------------------------------------------------------+\00"
+ at str.2 = private unnamed_addr constant [58 x i8] c"|                                                       |\00"
+
+declare i32 @puts(i8* nocapture readonly)
+
+; Check that we rematerialize the adr of str.1 instead of doing one adr and two
+; movs.
+
+; CHECK: adr r0, [[STR1:.LCPI[0-9]+_[0-9]+]]
+; CHECK: bl puts
+; CHECK: adr r0, {{.LCPI[0-9]+_[0-9]+}}
+; CHECK: bl puts
+; CHECK: adr r0, [[STR1]]
+; CHECK: b{{l?}} puts
+define void @fn() {
+entry:
+  %puts1 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.1, i32 0, i32 0))
+  %puts2 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.2, i32 0, i32 0))
+  %puts3 = tail call i32 @puts(i8* getelementptr inbounds ([58 x i8], [58 x i8]* @str.1, i32 0, i32 0))
+  ret void
+}
Index: lib/Target/ARM/ARMInstrThumb2.td
===================================================================
--- lib/Target/ARM/ARMInstrThumb2.td
+++ lib/Target/ARM/ARMInstrThumb2.td
@@ -1227,7 +1227,7 @@
   let DecoderMethod = "DecodeT2Adr";
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def t2LEApcrel   : t2PseudoInst<(outs rGPR:$Rd), (ins i32imm:$label, pred:$p),
                                 4, IIC_iALUi, []>, Sched<[WriteALU, ReadALU]>;
 let hasSideEffects = 1 in
Index: lib/Target/ARM/ARMInstrThumb.td
===================================================================
--- lib/Target/ARM/ARMInstrThumb.td
+++ lib/Target/ARM/ARMInstrThumb.td
@@ -1402,7 +1402,7 @@
   let DecoderMethod = "DecodeThumbAddSpecialReg";
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def tLEApcrel   : tPseudoInst<(outs tGPR:$Rd), (ins i32imm:$label, pred:$p),
                               2, IIC_iALUi, []>, Sched<[WriteALU]>;
 
Index: lib/Target/ARM/ARMInstrInfo.td
===================================================================
--- lib/Target/ARM/ARMInstrInfo.td
+++ lib/Target/ARM/ARMInstrInfo.td
@@ -2221,7 +2221,7 @@
   let Inst{11-0} = label{11-0};
 }
 
-let hasSideEffects = 0, isReMaterializable = 1 in
+let hasSideEffects = 0, isReMaterializable = 1, isAsCheapAsAMove = 1 in
 def LEApcrel : ARMPseudoInst<(outs GPR:$Rd), (ins i32imm:$label, pred:$p),
                     4, IIC_iALUi, []>, Sched<[WriteALU, ReadALU]>;
 


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