[libc] [gpu] Fix Minor Benchmark UI Issues (#102529)

Previously, `AmdgpuSinTwoPow_128` and others were too large for their
table cells. This PR shortens the name to `AmdSin...`

There were also some `-` missing in the separator. This PR instead
creates the separator string using the length of the headers.

Author: jameshu15869

libc/benchmarks/gpu/LibcGpuBenchmark.cpp

@@ -126,12 +126,14 @@ void print_header() {
   LIBC_NAMESPACE::printf("Running Suite: %-10s\n",
                          benchmarks[0]->get_suite_name().data());
   LIBC_NAMESPACE::printf("%s", RESET);
-  LIBC_NAMESPACE::printf(
+  cpp::string titles =
       "Benchmark            |  Cycles |     Min |     Max | "
-      "Iterations | Time / Iteration |   Stddev |  Threads |\n");
-  LIBC_NAMESPACE::printf(
-      "---------------------------------------------------------------------"
-      "--------------------------------\n");
+      "Iterations | Time / Iteration |   Stddev |  Threads |\n";
+  LIBC_NAMESPACE::printf(titles.data());
+
+  cpp::string separator(titles.size(), '-');
+  separator[titles.size() - 1] = '\n';
+  LIBC_NAMESPACE::printf(separator.data());
 }
 
 void Benchmark::run_benchmarks() {

libc/benchmarks/gpu/src/math/sin_benchmark.cpp

@@ -48,8 +48,8 @@ BENCH(NvSinVeryLarge, LIBC_NAMESPACE::__nv_sin, 30, 1000);
 #endif
 
 #ifdef AMDGPU_MATH_FOUND
-BENCH(AmdgpuSin, LIBC_NAMESPACE::__ocml_sin_f64, -1023, 1023);
-BENCH(AmdgpuSinTwoPi, LIBC_NAMESPACE::__ocml_sin_f64, -10, 3);
-BENCH(AmdgpuSinTwoPow30, LIBC_NAMESPACE::__ocml_sin_f64, 0, 30);
-BENCH(AmdgpuSinVeryLarge, LIBC_NAMESPACE::__ocml_sin_f64, 30, 1000);
+BENCH(AmdSin, LIBC_NAMESPACE::__ocml_sin_f64, -1023, 1023);
+BENCH(AmdSinTwoPi, LIBC_NAMESPACE::__ocml_sin_f64, -10, 3);
+BENCH(AmdSinTwoPow30, LIBC_NAMESPACE::__ocml_sin_f64, 0, 30);
+BENCH(AmdSinVeryLarge, LIBC_NAMESPACE::__ocml_sin_f64, 30, 1000);
 #endif