[PATCH] [mips] Always clobber $1 for MIPS inline asm.

[Toma Tabacu]

Hi dsanders,

Because GCC doesn't use $1 for code generation, inline assembly code can use $1 without having to add it to the clobbers list.

LLVM, on the other hand, does not shy away from using $1, and this can cause conflicts with inline assembly which assumes GCC-like code generation.

A solution to this problem is to make Clang automatically clobber $1 for all MIPS inline assembly.
This is not the optimal solution, but it seems like a necessary compromise, for now.

http://reviews.llvm.org/D6638

Files:
  lib/Basic/Targets.cpp
  test/CodeGen/mips-constraint-regs.c
  test/CodeGen/mips-constraints-mem.c
  test/CodeGen/mips-inline-asm-modifiers.c
  test/CodeGen/mult-alt-generic.c

Index: lib/Basic/Targets.cpp
===================================================================
--- lib/Basic/Targets.cpp
+++ lib/Basic/Targets.cpp
@@ -5749,8 +5749,8 @@
   }
 
   const char *getClobbers() const override {
-    // FIXME: Implement!
-    return "";
+    // FIXME: Are there any other registers which should be clobbered ?
+    return "~{$1}";
   }
 
   bool handleTargetFeatures(std::vector<std::string> &Features,
Index: test/CodeGen/mips-constraint-regs.c
===================================================================
--- test/CodeGen/mips-constraint-regs.c
+++ test/CodeGen/mips-constraint-regs.c
@@ -9,7 +9,7 @@
   // 'c': 16 bit address register for Mips16, GPR for all others
   // I am using 'c' to constrain both the target and one of the source
   // registers. We are looking for syntactical correctness.
-  // CHECK: %{{[0-9]+}} = call i32 asm sideeffect "addi $0,$1,$2 \0A\09\09", "=c,c,I"(i32 %{{[0-9]+}}, i32 %{{[0-9]+}}) [[NUW:#[0-9]+]], !srcloc !{{[0-9]+}}
+  // CHECK: %{{[0-9]+}} = call i32 asm sideeffect "addi $0,$1,$2 \0A\09\09", "=c,c,I,~{$1}"(i32 %{{[0-9]+}}, i32 %{{[0-9]+}}) [[NUW:#[0-9]+]], !srcloc !{{[0-9]+}}
   int __s, __v = 17;
   int __t;
   __asm__ __volatile__(
@@ -20,7 +20,7 @@
   // 'l': lo register
   // We are making it clear that destination register is lo with the
   // use of the 'l' constraint ("=l").
-  // CHECK:   %{{[0-9]+}} = call i32 asm sideeffect "mtlo $1 \0A\09\09", "=l,r,~{lo}"(i32 %{{[0-9]+}}) [[NUW]], !srcloc !{{[0-9]+}}
+  // CHECK:   %{{[0-9]+}} = call i32 asm sideeffect "mtlo $1 \0A\09\09", "=l,r,~{lo},~{$1}"(i32 %{{[0-9]+}}) [[NUW]], !srcloc !{{[0-9]+}}
   int i_temp = 44;
   int i_result;
   __asm__ __volatile__(
@@ -32,7 +32,7 @@
   // 'x': Combined lo/hi registers
   // We are specifying that destination registers are the hi/lo pair with the
   // use of the 'x' constraint ("=x").
-  // CHECK:  %{{[0-9]+}} = call i64 asm sideeffect "mthi $1 \0A\09\09mtlo $2 \0A\09\09", "=x,r,r"(i32 %{{[0-9]+}}, i32 %{{[0-9]+}}) [[NUW]], !srcloc !{{[0-9]+}}
+  // CHECK:  %{{[0-9]+}} = call i64 asm sideeffect "mthi $1 \0A\09\09mtlo $2 \0A\09\09", "=x,r,r,~{$1}"(i32 %{{[0-9]+}}, i32 %{{[0-9]+}}) [[NUW]], !srcloc !{{[0-9]+}}
   int i_hi = 3;
   int i_lo = 2;
   long long ll_result = 0;
Index: test/CodeGen/mips-constraints-mem.c
===================================================================
--- test/CodeGen/mips-constraints-mem.c
+++ test/CodeGen/mips-constraints-mem.c
@@ -9,7 +9,7 @@
  // 'R': An address that can be used in a non-macro load or stor'
  // This test will result in the higher and lower nibbles being
  // switched due to the lwl/lwr instruction pairs.
- // CHECK:   %{{[0-9]+}} = call i32 asm sideeffect  "lwl $0, 1 + $1\0A\09lwr $0, 2 + $1\0A\09", "=r,*R"(i32* %{{[0-9,a-f]+}}) #1,
+ // CHECK:   %{{[0-9]+}} = call i32 asm sideeffect  "lwl $0, 1 + $1\0A\09lwr $0, 2 + $1\0A\09", "=r,*R,~{$1}"(i32* %{{[0-9,a-f]+}}) #1,
 
   int c = 0xffbbccdd;
 
Index: test/CodeGen/mips-inline-asm-modifiers.c
===================================================================
--- test/CodeGen/mips-inline-asm-modifiers.c
+++ test/CodeGen/mips-inline-asm-modifiers.c
@@ -7,9 +7,9 @@
 
 typedef int v4i32 __attribute__((vector_size(16)));
 
-  // CHECK: %{{[0-9]+}} = call i32 asm ".set noreorder;\0Alw    $0,$1;\0A.set reorder;\0A", "=r,*m"(i32* getelementptr inbounds ([8 x i32]* @b, i32 {{[0-9]+}}, i32 {{[0-9]+}})) #2,
-  // CHECK: %{{[0-9]+}} = call i32 asm "lw    $0,${1:D};\0A", "=r,*m"(i32* getelementptr inbounds ([8 x i32]* @b, i32 {{[0-9]+}}, i32 {{[0-9]+}})) #2,
-  // CHECK: %{{[0-9]+}} = call <4 x i32> asm "ldi.w ${0:w},1", "=f"
+  // CHECK: %{{[0-9]+}} = call i32 asm ".set noreorder;\0Alw    $0,$1;\0A.set reorder;\0A", "=r,*m,~{$1}"(i32* getelementptr inbounds ([8 x i32]* @b, i32 {{[0-9]+}}, i32 {{[0-9]+}})) #2,
+  // CHECK: %{{[0-9]+}} = call i32 asm "lw    $0,${1:D};\0A", "=r,*m,~{$1}"(i32* getelementptr inbounds ([8 x i32]* @b, i32 {{[0-9]+}}, i32 {{[0-9]+}})) #2,
+  // CHECK: %{{[0-9]+}} = call <4 x i32> asm "ldi.w ${0:w},1", "=f,~{$1}"
 int b[8] = {0,1,2,3,4,5,6,7};
 int  main()
 {
Index: test/CodeGen/mult-alt-generic.c
===================================================================
--- test/CodeGen/mult-alt-generic.c
+++ test/CodeGen/mult-alt-generic.c
@@ -17,7 +17,7 @@
 // CHECK: @single_m
 void single_m()
 {
-  // CHECK: call void asm "foo $1,$0", "=*m,*m[[CLOBBERS:[a-zA-Z0-9@%{},~_ ]*\"]](i32* {{[a-zA-Z0-9@%]+}}, i32* {{[a-zA-Z0-9@%]+}})
+  // CHECK: call void asm "foo $1,$0", "=*m,*m[[CLOBBERS:[a-zA-Z0-9@%{},~_$ ]*\"]](i32* {{[a-zA-Z0-9@%]+}}, i32* {{[a-zA-Z0-9@%]+}})
   asm("foo %1,%0" : "=m" (mout0) : "m" (min1));
 }

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