[PATCH] D42401: [ARM] Expand long shifts for Thumb1 to __aeabi_ calls

[Weiming Zhao via Phabricator via llvm-commits]

weimingz created this revision.
Herald added subscribers: llvm-commits, kristof.beyls, javed.absar, aemerson.

For long shifts, the inlined version takes about 20 instructions on Thumb1. To avoid the code bloat, expand to __aeabi_ calls if target is Thumb1.


Repository:
  rL LLVM

https://reviews.llvm.org/D42401

Files:
  lib/Target/ARM/ARMISelLowering.cpp
  test/CodeGen/ARM/shift-i64.ll


Index: test/CodeGen/ARM/shift-i64.ll
===================================================================
--- test/CodeGen/ARM/shift-i64.ll
+++ test/CodeGen/ARM/shift-i64.ll
@@ -1,7 +1,9 @@
 ; RUN: llc -mtriple=arm-eabi %s -o - | FileCheck %s
+; RUN: llc -mtriple=armv6m-eabi %s -o - | FileCheck %s --check-prefix=EXPAND
 
 define i64 @test_shl(i64 %val, i64 %amt) {
 ; CHECK-LABEL: test_shl:
+; EXPAND-LABEL: test_shl:
   ; First calculate the hi part when the shift amount is small enough that it
   ; contains components from both halves. It'll be returned in r1 so that's a
   ; reasonable place for it to end up.
@@ -22,29 +24,34 @@
 ; CHECK: lsl r0, r0, r2
 ; CHECK: movge r0, #0
 
+; EXPAND: bl __aeabi_llsl
   %res = shl i64 %val, %amt
   ret i64 %res
 }
 
 ; Explanation for lshr is pretty much the reverse of shl.
 define i64 @test_lshr(i64 %val, i64 %amt) {
 ; CHECK-LABEL: test_lshr:
+; EXPAND-LABEL: test_lshr:
 ; CHECK: rsb [[REVERSE_SHIFT:.*]], r2, #32
 ; CHECK: lsr r0, r0, r2
 ; CHECK: orr r0, r0, r1, lsl [[REVERSE_SHIFT]]
 ; CHECK: sub [[EXTRA_SHIFT:.*]], r2, #32
 ; CHECK: cmp [[EXTRA_SHIFT]], #0
 ; CHECK: lsrge r0, r1, [[EXTRA_SHIFT]]
 ; CHECK: lsr r1, r1, r2
 ; CHECK: movge r1, #0
+
+; EXPAND: bl __aeabi_llsr
   %res = lshr i64 %val, %amt
   ret i64 %res
 }
 
 ; One minor difference for ashr: the high bits must be "hi >> 31" if the shift
 ; amount is large to get the right sign bit.
 define i64 @test_ashr(i64 %val, i64 %amt) {
 ; CHECK-LABEL: test_ashr:
+; EXPAND-LABEL: test_ashr:
 ; CHECK: sub [[EXTRA_SHIFT:.*]], r2, #32
 ; CHECK: asr [[HI_TMP:.*]], r1, r2
 ; CHECK: lsr r0, r0, r2
@@ -54,6 +61,8 @@
 ; CHECK: asrge [[HI_TMP]], r1, #31
 ; CHECK: asrge r0, r1, [[EXTRA_SHIFT]]
 ; CHECK: mov r1, [[HI_TMP]]
+
+; EXPAND: bl __aeabi_lasr
   %res = ashr i64 %val, %amt
   ret i64 %res
 }
Index: lib/Target/ARM/ARMISelLowering.cpp
===================================================================
--- lib/Target/ARM/ARMISelLowering.cpp
+++ lib/Target/ARM/ARMISelLowering.cpp
@@ -820,6 +820,13 @@
   setOperationAction(ISD::SRA,       MVT::i64, Custom);
   setOperationAction(ISD::INTRINSIC_WO_CHAIN, MVT::i64, Custom);
 
+  // Expand to __aeabi_l{lsl,lsr,asr} calls for Thumb1.
+  if (Subtarget->isThumb1Only()) {
+    setOperationAction(ISD::SHL_PARTS, MVT::i32, Expand);
+    setOperationAction(ISD::SRA_PARTS, MVT::i32, Expand);
+    setOperationAction(ISD::SRL_PARTS, MVT::i32, Expand);
+  }
+
   setOperationAction(ISD::ADDC,      MVT::i32, Custom);
   setOperationAction(ISD::ADDE,      MVT::i32, Custom);
   setOperationAction(ISD::SUBC,      MVT::i32, Custom);


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